A few of notes:
1) Mab is a well known twister of words. When she is asked who kidnapped Marcone, she replies she does not know. That could be true if she knew the Denarians were responsible for the kidnapping, but not which individual was precisely responsible for subduing and binding Marcone.
2) Alternatively, she could suspect that some of the Denarian are working for the Black Council and not Big Bad Boss, thus "who" took them is up for debate.
3) It is entirely possible that Mab and Uriel are working far closer than suspected here, more than just a common enemy might allow for. One could argue that the entire reason Mab chose Harry was to get the archive involved so that Uriel would be given an opportunity to become involved.
It still doesn't answer how Mab got everything moving before the initial attack, however. Unless the Denarians were using Ways she could time-delay....