Our AIP says:
Aircraft must be fitted with a serviceable Mode A and Mode C, or Mode S, SSR transponder for operations as follows:
- All aircraft within classes A, B and C airspace, and any class of airspace at or above 10,000FT AMSL.
- All aircraft, except aircraft operating to the VFR which are not fitted with an engine driven electrical system capable of continuously powering a transponder, within Class E airspace below 10,000FT AMSL.
So the answer to your question, here at least, would be "enroute prcoedures
do require it's use", therefore she's a No Go item.