KotS is no longer based on that engine. It was first planned to be based on a largely upgraded IL2-engine, but then it was clear they had to overcome some limitations. According to their forum they dropped the IL2-engine and came up with something else. So I doubt it's the BoB-engine.
@ HenFre
No, I'm not part of 1C, nor am I otherwise involved in the project other than providing some resources. But I'm with the flight-sim-genre in general for long enough to know where to look for that sort of information.
@ VMF-214_HaVoK
I read in a forum that a FlyingTigers-Simulation was being worked on and I concluded from the context that it was the sim Shockwave is working on. When they were recruiting I was invited to write an application, too, and the little information they gave me as a bait would fit the Flying Tigers setting.