Yes, an articulated bus. There are none in my state so all P endorsements here are restricted. I’ve never seen an articulated Greyhound, but I guess they could have some. Some large cities have them, but not here.
Not exactly. An articulated bus is not a class A bus, it is still a class B vehicle because the vehicle is not designed to split and the driver is not isolated from the passengers. A class A bus is a true tractor and trailer with a conventional 5th wheel, driver in a isolated compartment within the tractor and a means of communication between the passenger compartment and the driver compartment. There are virtually no class A buses in use in North America anymore, the license is a hold over from a bygone era.
If you look at the attached image of Figure 1 from Part 383.91 it clearly shows the image of a class A bus as a tractor trailer and an articulated bus as a class B.
That is state specific. Here in PA I can administer a new road test in a class B with a manual to remove the E (auto only) restriction and they retain their full class A. For the out of state applicants we can administer the road test to the same holds true, however the rules may be different testing within their home state. The reciprocity agreement that allows testing out of state makes allowances for minor variations in procedure as long as the base test is the same.