You don't have to use a client supporting Oscar or TOC to use AIM. You can do it from your Jabber/XMPP client by using an AIM transport. The transport becomes a proxy for your AIM account and permits you to register on their service, using your Jabber/XMPP client. I think ideally Jabber wants to do away with transports eventually, as the quality of them vary and let's face it, they're not very elegant, proprietary IM protocols not withstanding.
But, with this deal, I could see AOLand/or Google, setting up a custom XMPP-AIM gateway that would probably only allow s2s communication from Google Talk and any one else they let into their proposed "federation." This would allow all their users to communicate with AIM users and vice versa.
Though, I'm not too keen on Google's federation, either. Limiting s2s connectivity only to networks they choose, goes against one of Jabber's primary advantages -- IM decentralization. One of the big advantages to Jabber, is having an open protocol which finally gives the Internet community a way to decentralize IM. Just as so many other open protocols before it have enriched the Internet of today.
Requiring third party networks to federate, in order to interoperate with Google Talk only makes sense, IF they're using an incompatible protocol. Jabber/XMPP s2s communications, however, would be compatible as they're all ready using a subset of the protocol that Google Talk natively uses! So, Google, if you're reading this, what gives? Show the world just how much you believe in openness, and allow anonymous s2s.