Nil,
If you were not implying that the experience of the crew (2000h) was not part of the RTO then why mention it??
Anyhow, to answer your question about driftdown, generally and for CAA calcs, the worst case Driftdown I think, at ISA +15c conditions is 18,000ft. This has never been its issue since I have flown the Zurich- Odina run. It is more to do with the lack of drop down oxygen and the requirement to be at 14,000ft within 4 minutes. This rather puts a limit on which parts of the alps you can traverse.