Cheap and expendable = ideal for track IME but no they're not 888s or similar. When I've had track cars I've driven to the track on good road tyres and then fitted track wheels fitted with cheap s**t tyres to burn off. Running 888s got expensive quickly and didn't really add a benefit to anything other than lap time.
I did have them checked when they were removed and was told they were OK for MOT (they were removed at a garage which does MOTs). If they weren't I wouldn't have listed them without mentioning that fact.