Moveable Do-Re-Mi?

Recently, there is an ongoing discussion in our Turkish Maqam Music programmers group Notayaz concerning the application of the solmization as described here:

http://www.answers.com/topic/solfege

The reference is to a `moveable Do` practice aside from fixed C, which my Turkish colleagues defend can be applied to any instrument and any voice (as is being done with G taken as Rast and sounded as D in `standard` Bolahenk diapason), against which I claim that the only moveable Do (or C, since they are both nailed down to the international diapason standard) can be implemented via Key Transposition through only those instruments whose key systems do not change despite their size, such as Bb Clarinets or English Horns.

Besides, Rast (first pitch of the sound system) should definitely be Do (C), which the Yekta-Arel-Ezgi tradition clearly violates.

However, I encountered that, during the early stages of learning solfege, the student is guided to keep Do-Re-Mi syllables in the diatonic scale while changing the diapason... hence attributing the same order of spelling with both C Major and F Major.

I interpret this as an attempt to reconcile between practice and theory... particularly since there is no C-D-E pronounciation in Turkish, and the only means available to sing notes is by way of Do-Re-Mi.

Is it permissable to sing Sol-La-Si (written G-A-B on the staff) while the syllables sound as D-E-F# according to the standard diapason?

Cordially,
Ozan Yarman