I mount meterbase/service equipment before brick all of the time. I fabricate a mounting bracket from 1/4" x 2" angle iron and bolt it to the plywood/OSB. It stands the equipment off of the sheeting 4-1/2". This allows the brick to be layed up behind the equipment leaving a gap to be caulked when they are finished.
Our uitlity would not accept that, even as a temporary service, only the published specs, in the utility installation handbook are approved.
I tried that stunt once, and the utility cut the service. I can see their issue, a powered up service before the equiment base construction is complete, is asking for an accident.
