That doesn’t sound likely. That would mean AOL would have to be capable of giving every AIM user a phone number.
As far as I know, there’s no way for someone to, from a cell phone, without logging into AIM via text message, start an instant message with a logged in AIM user.
The SMS-based AIM service requires you to text log-in credentials to an AIM phone number. Once you do that, it keeps track of your phone number. Whenever someone IMs your screen name (you appear online once you do this) the IMs are forwarded to your cell phone as text messages.
In order to see who’s online, you have to send the service a message telling it to show you your buddy list (who’s online), and it returns with a text message containing your buddy list. You can choose who to IM from here, by texting back which person on your buddy list you want to send a message…
The whole thing is very cumbersome and is only really feasible if you have an unlimited texting plan.