While on ADOS for a reserve CMD, assigned to another reserve unit, does a soldier have to attend BA with the unit they are on ADOS for?

You are usually not required to attend the BA for the other unit. It may differ if that unit is part of the command for the one on ADOS. Another it depends on the mission in the National Guard soldiers are on ADOS orders for Homeland Response Force (HRF) but, are required to attend BAs for their unit. Also, keep in mind once of ADOS you might being going back to that unit and, not a good idea to burn bridges or anger the other unit. It could come back and bite you in the ***.

while on active duty orders you do not get paid additional time for BA, but do have to work BA weekends if the duty requires it. this is the same as AGR soldiers who have to work BA Weekends.

A friend of mine in the Georgia Guard was on ADOS orders and he did have to drill with his unit, but I have not seen that in the Reserve.