I had to check that we are talking about a G.992.{1|3|5} service and not a G.993.2 (VDSL2) service . . .
With a separate modem and router, powering off the router will just cause your ISP/CP's systems to note that you have dropped the PPPoA connection. The exchange based MSAN (or DSLAM) will not have any knowledge of that upper software layer and so will happily continue "talking" to your modem.
So the answer to your question is "no".