I thought that as long as the higher class license holder is physically present at the control point, the lower class licensee could use the equipment and operate on bands that the higher class lic. has privileges on.
This is correct, as long as the higher class licensee is the control op.
What ever the Operating privileges of the control Op are, can be used by ANYONE, even a non License holder, for example, a school student with no licenese, can work HF if the control lic holder has Privileges in that band.
It is the control op`s responsibility to make sure all rules are followed.
That is why the "control operator " must be present, he or she must be there as to have "physical control" of the station so as to be able to stop transmiting if the rules are broken.
It does not matter whose equipment it is, yours, his, or belonging to ARRL headquarters.
So Yes, if you go to your friends house, and ID as the control op, with your call sign, he can use the same bands, modes and so on as you have as long as you are present to act as the control op.
You must still ID as the control op every ten min, just as you do when you are using the radio.
This is WB6*** controlling
Hand him/her the mic, let them talk, at 10 min intervals, or the end of the QSO, you ID......
this is WB6*** controlling
This ID`s YOU as the control op, and tells everyone that YOU are responsible for the station control.
73
Jeff