I think the key factor is the concept/design phase. To the best of my knowledge, Carmatech did their design work in secret (since nobody had even heard of them until PB extrav.). So, it would come down to who conceptualized / designed it first (and has documentation to support such claims).
In other words, if RAP4 has documented proof that they developed theirs, independently, before Carmatech filed for patent then, they have a chance. Otherwise, they are at Carmatech's mercy.