Respell Pitches command changes only concert pitch spelling, regardless of current state
2.0, Ubuntu 14.04
1) score for Bb and concert pitch instrument, key of Eb concert
2) on staff for Bb instrument (key is F), enter an A#
3) on staff for concert pitch instrument (key is Eb), enter a G#
4) select all
5) Notes / Respell Pitches
Result: nothing appears to happen, but switch to Concert Pitch mode, and you'll see the pitches were changed there.
This command should probably affect both tpc1 & tpc2, just as I hjave proposed the "J" command (see #51886: Enharmonic change made using "J" on concert pitch instrument not saved).