Collaboration, probably not, but there was definitely existing knowledge of the attackers and they were under surveillance for a long ass time.

Lots of people say that the CIA and FBI were just incompetent and/or underfunded (I'll give you incompetent), but that's a hugely convenient fuckup for a lot of people involved, like Cheney and Bush that were looking for a casus beli and they just happened to get the perfect one in the first year of their rule.