I guess this is a case where you need to be "proactive instead of reactive" (used by scheds more than once).

When told you can't depart until the other a/c has left, call scheds and ask if you are on STBY.

If they say yes - then have it added to the pairing.

If they say no - then tell them you would like to depart as scheduled!

If it is a "schedule change" and they knew about it ahead of time - ask them why your pairing and show time were not changed!

Then submit a POR or whatever it's called now. If enough are submitted eventually it may change the way they jack us around at times!