I'll re-introduce my own WAG here... part of which is that Justin isn't (necessarily(*)) the "evil wizard" Harry thinks he is.
He's "old-school" and harsh, for sure... fastball baseballs as shield-training, &c. But the mover & shaker in this was Mab(**).
She knew the Starborn Cycle was cresting, and that Outsiders would be making a special push. Mab wanted a Starborn as Knight (and likely in other roles too), so she "arranged" for Maggie LeFay to:
- "discover" the Starborn cycle & hints of a "starbabe"plan
- "accidentally" meet the Leanansidhe on multiple occasions, sufficient for Maggie to think of Lea when she needed a protector for Harry
Then she stepped in when Malcolm died, to hide Harry from everyone searching (foreshadowed, story-wise, by Morgan being anti-scry'ed by Summer)... until Harry's gifts showed, and it was time to get him trained.
Then -- and this is where it gets relevant to this thread -- she got Justin to do the training (either by tricking him, or as repayment for debts-incurred); note how Justin's "harsh" training was often thematically-similar to a "Winter"-driven harsh training.
(*) Critical counter-datum on the "Justin
is evil" front: taking Kemmler's "EvilBob lab-assistant" skull as his own, hiding it from the WC (***)
(**) Mab and/or her handmaid, Lea
(***) On the third hand, I'll introduce another WAG -- Bob isn't really "afraid" of Mab/Winter; he's an active _agent_ of Winter, one of Mab's spies amongst mortal wizards / the White Council. Justin, in this analysis,
rescued the skull on the orders of Mab (much as Harry got the Word of Kemmer on Mavra's orders): Mab got the skull to Justin so that he could get it to Maggie's Starbabe (which plan was already underway at the time of the final Kemmler-fight) in a way that didn't even
hint at a faerie affiliation.