Yes the Monza's are BBS wheels (some Monza's are made/have been made by Ronal) and no the genuine BBS caps won't fit I'm afraid.
BBS caps only come in 3 sizes, 1 is 56mm and IIRC the others are 70mm and 80mm (front face diameter) and the Monza'a are 65mm. Someone will be along to correct me if I'm wrong.