We'll know that BP-Ascension and SCSII don't work together when the first people complain about it in detail. Or more precise: Some people told me (and I experienced by mysel) that they (I) had problems with SCSII and BP-Ascension, but this was limited to certain installations (possible to reproduce, but very seldom) and one had problems with mages from the very beginning. Other people told me that it would work. [Always NOT using BP AI-component).
I made a quick test with my small tactic-installation and Illasera (or however she's called... the bhaalspawn in the ancient's grove) and her group have SCSII AI and killed me in some seconds. This doesn't mean that there couldn't be glitches. (I'm quite sure I'll find some...). I'm currently testing my installation, but I'm in Nashkel, so don't expect information too soon... At the moment I'd say: If one doesn't have problems in
BG1 and in the ancient's grove, one should give it a try...
(Maybe the BP-scripts are all in the AI component and don't get installed, so SCSII doesn't have problems. Maybe SCSII is compatible with some BP-scripts, as it was before the update. Hm... I'll see...)