Lizard said:3e: Rules state what aboleths can do. DM may decide to alter these rules, but if he's caught unawares or doesn't care, he has something to work from.
4e: (As per OP; we don't know for sure) Rules state bupkis. DM has that much extra work to do before using a creature; players have that much extra learning to do.
That you require a rigid framework before using a monster is your problem, and one which can be solved simply by not thinking too hard about fantasy.