Apparently, their plan will include identifying heavy users during a period of congestion, then de-prioritizing those users as compared to the rest of the network for 10-20 minutes. Furthermore, someone who habitually uses large amounts of bandwidth won't get singled out – the throttling is all done on a per-case basis. The throttling won't affect any particular program or traffic type, and will instead simply slow down the entire connection.
This is certainly a more fair approach than any other that has been proposed so far. A “heavy user” is determined on a per-minute basis, avoiding singling people out, and the connections aren't shut off, merely slowed. However, it does bring to mind another question – just what is “heavy use”? As we've seen in recent days, some ISPs have very limited ideas of what a heavy user is. Ultimately it's an issue of perception – and it seems people will have to trust the ISP to make the right decision.