[Scan-DC] MAV, or MAB?

[Doug Kitchener via Scan-DC]

OK, Montcamera County has two, count 'em, two, of these "Medical Ambulance Buses", thanks to the generosity of Homieland Security.  But it sounds to me that their call signs are MAV rather than MAB... anyone know which one it really is?

https://www.google.com/search?q=montgomery+county+medical+ambulance+bus&tbm=isch&tbo=u&source=univ&sa=X&ei=9oPjVMitDuvZsATnyYHwBg&ved=0CB8QsAQ&biw=1152&bih=751

Station 51, KMG-365