If it doesn't say "Initializing accompaniment engine..." (or something similar) than it means the BIAB functions aren't being initialized, so I'm not sure why it would be slow at startup if you don't see such a message.
Now that you mention this, Jeff... I have a question.
I have a bunch of songs for gigs that I load one at a time. MOST of them load quickly. Every now and then one of the project files generates the message above "initializing accompaniment engine..." and the song takes a lot longer to load.
What puts that in motion? It happens on the same files, every time. In playback mode, I'm not invoking any of the features used to generate real content, so I guess that's why I don't usually get that message until I reach certain files.
I have started over and recreated some of the problem files and the message went away... but if there's an easier thing to identify and remove, I'd rather do that.
Its bad Juju standing in front of a live audience waiting for a song to load. ;-)