Did they ever find a use for these things? BMPTs are notorious for not fitting into any sort of doctrine.

Honestly, I agree with the opinion that this BMPT was just a way to grab some money. The fact that the military alraedy had a ready prototype (Object 787) that was better protected, better armed and could be manufactured with way less hassle i.e. more parts were similar with a T-72AV, tells me that someone just wanted to reinvent the bicycle and make some dosh. Let alone that this kind of vehicle had no place on the battlefield altogether.
Pic related: