To answer the question, I've only seen Princess mentioning which locks its ships sail through, and only the Island Princess will go through the old locks.
Look up PANAMAX size and then compare that with the size of the ship doing the transit. If it is smaller than Panamax, one blogger says that it's a good bet that the ship is using the old locks. (Larger ships must transit the new ones due to their size.) If the ship can handle 2000 passengers or less, that is another good indicator. But I wouldn't trust anything not published by the cruise line. So I'm asking the lines themselves about which locks will be used for the cruise, as I don't want to waste my time making half assed guesses....
