I'd like to pose a question to the 403(b) plan practitioners:

When 403(b) plan deferrals are matched to a 401(a) qualified plan, what are the mechanics of the ACP test?

There's clear, substantial authority concerning ACP testing of matching contributions made to a 403(b) plan (i.e. when the plan receives both the employee salary reductions and the employer match). But, I haven't found an answer for 403(b) plans and QPs that work in tandem. Do you treat the matching contributions as if they'd been made to the 403(b) plan (rather than to the QP) and perform the test accordingly?