The only other thing I have found concerning navaids and their use as primary nav under IFR is this excerpt from AIM Chapter 1...

AIM 1-1-19 (e) - "Use of GPS for IFR Oceanic, Domestic En Route, and Terminal Area Operations"
(2) "GPS domestic en route and terminal IFR operations can be conducted as soon as proper avionics systems are installed, provided all general requirements are met. The avionics necessary to receive all of the ground-based facilities appropriate for the route to the destination airport and any required alternate airport must be installed and operational. Ground-based facilities necessary for these routes must also be operational.

This could call into question exactly how an unmonitored navaid relates to an operational NAVAID. The way I figure is that since the FAA tells us about non-operational navaids by means of the "OTS" NOTAM notation, I tend to think that unmon DOES NOT constitute a navaid NOT being operational simply because if the FAA wanted to tell a pilot that a navaid was Out of Service, then they would NOTAM it "ABC VOR OTS" not "ABC VOR UNMOM!" Although this sounds good to me, I do concede that there is a certain level of ambiguity between Operational and Unmonitored simply because the FAA doesn't tell us anywhere EXACTLY what unmonitored means.