There are entertainer coaches that do not have commercial plates because they are privately owned. I believe most are owned by leasing companies and carry all the licenses and certificates. But the privately owned coaches are what has begun to attract attention. I am not sure what the officials are looking for, but that skirting of the law likely has now focused attention on all bus conversions. Once anyone sharper than a door knob sticks their head in the door they know it is not a RV or motor home. From that point on they know as a commercial bus they need a fresh box of BIC pens for all the tickets they can write.
Ironically two identical rigs can have to meet completely different rules regarding their operation.