Yes, yes, I know, the old days were best.
I do not imagine that the standards required to get Part 147 Cat A Basic Training approval are any different for an agency than for an airline or college, of which several hold Basic Training approval.
We can reflect on the fact that the MTOs with the worst compliance standards that I have seen by a country mile, in the UK at least, are those set up by licensed engineers to sell type training only.
Agencies have been involved for many years in at least 2 MTOs with Basic Training Approval, one of which operates to very high standards to my certain knowledge, and the other probably does but I don't know them well.