Hello Thomas,
It has been a while so you might not even be here anymore, nevertheless I will try to help. I am from Syria, so to answer your question: in Standard Arabic you must say راحت الباصات so this is 3rd person feminine singular. But in my dialect we say: راحوا الباصات which is 3rd person masculine plural.
Let me know if this helps, contact me if you need help :)
Cheers,
Ahmad