Sometimes they are listed for international destinations, but in most cases you are expected to call your appropriate elite hotline or regular reservations (1-800-433-7300).

Most of the time, the PLT desk can help you better than airport agents anyway (even better than AC agents).

But, in some cases, the PLT agents won't have access to the most up-to-date information about things like airport-specific baggage embargoes and restrictions. When you need this kind of first-hand information, the best thing to do is call the AC at that airport, tell the receptionist that you are a member, and ask him/her to call the ticket counter for you to ask the question. Usually they are happy to oblige.

For example, the last time I was flying out of JFK to the Caribbean, I spoke with the PLT desk and they said that there was no luggage restriction, just an embargo on boxes. But, when I asked the AC agent to check with the ticket counter, I found out that, YES, there WAS a luggage restriction--no overweight/oversized permitted.

So, it just goes to show that:
1) Most of the time you can get the info you need from the PLT desk; but
2) Sometimes you NEED to get first-hand information from the agents who will be checking you in.

If you need the kind of information in #2, either visit the airport in advance or do what I did. Or call your Special Services/Premium Services phone number if you have access.