So after reading this and rereading this thread I think that good points have been made by all contributors and though you might say "It says this right there..." I believe that The APA has provided no clear definition of Regular Shooting Cue and Break Cue, so interpreting the rules regarding switching cues and the specialty shots has become a little muddy. There are just too many arguements to be made on both sides.
The WPA and BCA have identical definitions and it appears to be a much simpler question at that level, as if to say "This is a cue, you play pool with it, and the game starts like this, now go play".
Because The APA caters to the lower level player and would rather not give a distinct advantage to a more senior level player, at least not by means of equipment (or the "Push Out") there is a rule or definition for both a Playing cue and a Breaking cue. I see now neither is terribly clear.
A short time ago there was a thread "What Makes a Break Cue a Break Cue?"
http://forums.azbilliards.com/showthread.php?t=415762
Ther were only a couple of pages of responses, weight, shaft, tip, etc.... some became a little more scientific as to speed + weight striking mass..... and stuff like that, but still no clear definition.
The final post was from "ivicafranic" who simply posted "The guy who breaks with it". I think that may be closest thing to a right answer, at least from my perspective.
For purposes of interpreting The APA rules, it still isn't terribly clear. My personal contention is that you shoot with what you brought to the table. I don't really care which cue you bring to the table to start your half of the inning, but unless there is some damage to the cue or it is the break shot there will be no switching cues in the middle of your turn As a referee that is how I have ruled on this in the past. Reading this thread has compelled me to rethink that position, but frankly I don't think The APA can even really agree on this, yet.
As an athlete (or pool player) I have certain things that I have always reminded myself of: Know your opponent, know what to expect and rely on the percentages, Know my own limitations, don't be stupid, and Know the rules, they can save you.
I think as APA players some of us tend to let the rules play the game for us and we don't rely on our own skill as a player to win a game. My role as a referee is a little different from my role as a player. I'm well aware of the rules and as a referee I'm there to help you play within those rule if you should have questions about them. As a player, as long as we play like gentlemen it's all good and I really don't care what stick you bring to the table and when you might switch it out and regardless of what the rules are. As long as we play by the same rules there won't be a problem.
I think, that at least for me, this will require a little more research, it's not as simple as it looks.