I don't think it's a completely unreasonable idea, but any motor intended for a bus is likely to be quite large. As an advantage, it may be capable of producing a lot of torque so it could be used to drive the rear axle of a traditional car, without any other reduction gearing. Some battery-electric buses have been commercially produced with motors that are lower-powered than typical current electric cars... it might not be unreasonable.
Do you have a specific bus motor in mind?
Do you have a specific bus motor in mind?