Yeah, I see her response being, "You have a problem with the local authorities? Well, deal with it. I can't have my Winter Knight incapacitated." If Harry gets locked up, she'll probably just pluck him out of prison into the Nevernever, and then he'll have to deal with being a fugitive. He'd end up living mostly in the Nevernever and/or Demonreach.

Mab has a vested interest in the Mortal realm. Faerie is so closely tied that she controls the weather. Deals with Mortals increase her power. Deals with mortals of power even more so. There is a reason she wants her hooks in Harry. I am more than certain that Mab could make a Deal with the right people if she chose to do so. She has some knowledge of what is to come, and knows Harry is central to it. Now Slate or some other throw away I can see her letting him rot. Plus she ALWAYS pays her debts.

Odin (Monoc) may not be what he once was, but that is not the same as powerless. He has clearly been preparing, and he has Foresight to make the right connections.

I could see Marcone helping Harry just to irritate him. It probably wouldn't cost him much, and the look on Harry's face would be priceless.

Murphy has clearly built up some power in Chicago. It may not be 'official,' but that does not mean it is insignificant. If nothing else Tilly trusts her, and will at least give weight to what she says.

Plus there are numerous others that have an interest in having Harry roam free. Even some of his enemies.

Now at the end of the BAT I could see him getting arrested just as he thinks everything is going to be alright. He beats the great cosmic evil, only to be finally arrested by Rudolph

Yanno 3E does seem like it could be a variation of the Gatekeepers eye ointment...

I've had this idea running about in my head lately that Harry is attuned to chaos and that is part what gives him his Outsiderbane abilities. You can't really command something in the DV without having an understanding of its nature. Much of what Harry has done has lead to more chaos than stability. His victories often just lead to more and greater chaos. He has the strongest (worst) 'murphyonic' filed of any wizard he has ever heard of, which strikes me as an effect of his chaotic nature. He has issues with controlling evocations even with proper Foci. There is a reason he causes so much property damage.

I am thinking that many of the powers out there are using his affinity for chaos to prepare the way so to speak. I think it might have been a part of the plan that Maggie Sr had worked out with Lord Raith.

Looking at the books it is clear that something/someone is trying to create more and more chaos and that they are putting Harry in the center of it for a reason (besides him being the protagonist of course ):

- SF someone tries to undermine Marcone. Who while not a really 'good' guy, he IS a stabilizing influence.  And Harry makes an enemy of Bianca.

-FM someone gives the belts to the FBI once again Marcone was a target. Arguably converting agents of law and order into ones of chaos.

-GP someone is defiantly setting the table for the future. Harry starts the war with the RCVamps because of the events that unfold. Plus it helps set up events in BR. 

-SK has elemental chaos in the works that ends up creating an imbalance between Summer and Winter. And sets up Harry to become the WK.

-DM it is out and out stated that the goal was to create a mini-pocolypse. Which while averted still lead to the loss of one of the Knights and to Harry taking up a Coin.

-BR lead to Harry giving the Word of Kemmler to Mavra and a major shake-up in the White Court. It also lead to the death of Ortega which has no small effect on future events.

-DB Here the Wardens are all but wiped out, Luccio loses her body which costs her ability and sets up future events, Mavra gets the Word of Kemmler, Harry voluntarily uses Hellfire and the help of the Fallen.

-PG This one is one of the few books that don't have a major increase in chaos or set up for greater future chaos at the end that I can think of. However, it does put Harry on the hook for Molly, sets up WK, and gives Harry and Morgan the Summer Court pins/favors.

-WK Has the culling and the death of numerous White Court higher-ups, the inclusion of Marcone as a signatory of the Accords, and the return of Cowl.

-SF Lots of things in this one as well, Michael getting lamed, the fracturing of the Denarians, Ivy getting abused, one of the Denarius dispersing, Marcone getting a job offer from Nic, and the introduction of Demonreach.

-TC Death of Morgan, death of several WC members, appointment of Christos to the SC, lots of fear created in the Wardens, Harry loses Lucio, the grey council is introduced, Thomas is abused, Harry claims DR as his Sanctum, Harry 'see's Shagnasty and almost loses it, and Kirby dies.

-C This entire book was about chaos and IMO had the most chaotic ending of any of them.

So what I am thinking, is that the BC endgame doesn't require Harry to lose, but rather is set up in such a way that his victories contribute to a growing amount of chaos, similar to the whose barb wire spell preparing the way for the Dark Hollow. Only on a much greater scale. They want Harry on their 'team,' but are clever enough to use his ability to 'understand/create chaos' without his 'consent.'