I am a "Division Rep" for my APA league. While there is no rule in the book about the cue ball, each league operator can enact local "bylaws". These are typically rules voted on by the reps and sent out to the captains at the beginning of each session. I don't know if this is specific to my league operator or something all league operators do. In any case, the bylaw for us is this:
The home team can provide any cueball they want. The decision about which cueball to use is made at the beginning of each *individual* match, but the home player always has the final say. So for example, say I bring my own standard cueball to another bar. I tell the team captain and he agrees to use it. We play match 1 and 2 with it. Say we get to match 3 and the home player says he would rather use the bar ball. Then the bar ball will be used for that match. When the 4th match is about to start, the home player can decide to go back to the real cueball or stick with the bar ball. However, once an individual match is begun with a cueball, that cueball must be used for the duration of the match.
Personally I don' think this is the best. I personally think the captains should agree before the match, and whatever ball is decided upon should be used throughout the night. This is because it *could* effect your decision to play certain players who are particularly good or bad with a heavy or oversized ball. It would not be fair to find out after you already put a player up the the conditions would change.
Most of the teams in my division use a real cueball. This could be partly due to the fact that I have a standing offer to any team in the division that if they wish to convert to a real ball, I will give them a Super Aramith Pro cueball for free, with the stipulation that they must use it every week at home. I laugh at some of the people who believe that playing with a large or heavy cueball gives them a "home field advantage". They haven't though the topic through very well. First of all, 50% of their matches are played away, so you could just as easily consider it the home field game ruiner. Also, they are really missing some fundamental aspects of the way position is played, and their games typically show it. Also, the regional and state championships are played with a standard cueball, so why not be very comfortable with it. Finally, what about the fact that the cueball is *SUPPOSED* to be the same size and weight as the other balls. Anything else is a bad solution to a problem (making the cueball return on a coin op table). Why would people voluntarily do things the wrong way?
Anyway, theres my longwinded answer ha ha!
KMRUNOUT