This seems an anomality that is peculiar to AOL (and tiscali).
BT actually did all the work to upgrade 99.99% of exchanges by the end of March 2006 and aside from 1 or 2 all exchanges are now Maxdsl enabled (up to 8Mb).
You can check when your own exchange was Max enabled by putting your details in the
adsl checker.
It should say something like "dsl Max enabled: March 30, 2006 "
AOL seem to be dragging their heels upgrading their customers on their side of things. The fact that you are already syncing at the higher speeds shows that you can get the higher speeds, just that AOL arent giving you the throughput.
The term they use
"these speed upgrades are performed on a bulk migration process and as such they work on a exchange by exchange process" sound more likely that they are referring to transferring lines to LLU.
Bit naughty the way AOL are going about this.. and the way theyve phrased the sentence
"that your line has now been upgrade to ADSL Max and that this will supply the highest stable speed that your telephone line is capable of" isnt quite true.
Yes your line has been upgraded - but AOL arent giving you the throughput speed that its capable of.
... but the main thing is that you are happy now that theyve given you the 2Mb that you requested