It is entirely possible that ATR has an approved ferrying procedure that allows this operation. As previously posted, the altitude limitation is a certification issue related to the pax ogygen limitation, it is not an aerodynamic nor engine operation limitation. MNPS equipment requirements are a moot point as there are enough loopholes in the current standard that allow VOR equipment as an acceptable means! On the other hand RVSM requirements were most likely the issue here as it is doubtful that an aircraft with a 25K limitation on altitude would have such certification. As always, waivers and exemption are available and routinely issued.