Certain models got certain licence.
I believe DD got a few types:
1) Volvo - Can drive VO with this
2) Leyland - Can drive LO with this
3) B9 - Drive B9TL and also operate the manual ramp with this
Other models that have their own licence are usually those WAB
buses like K230, or low floor ones like the B10BLE CNG. And not
forgetting the Superlong.
There is no VO or LO Licence. There is just DD licence. If a
driver is given a LO or VO which he doesnt like to drive, he can
always claim that he doesnt know how to drive.
As for the B9. There is no certain licence. Just that the BC
must go through a lesson so as to know the basic controls of the
Bus and on the operation of the ramp.