Both the company I now work for and my previous one had encountered instances of this, and both have had to stress that DH must be called solely upon Baro Alt.
RadAlts may be used for DH only for Cat II and III approaches.
The reason for this is that, on a Cat I approach (or, indeed, a non-precision approach, there is no guarantee prior to the threshhold that the ground does anything remotely predictable as you close on the runway. You may, therefore, go from 500' Rad to 30' Rad in the blink of an eye.
Hence use of the RadAlt for non-precision approaches is NOT a safe practice.