it isn't a surprise Alfa Romeo said it isn't possible - what they actually meant is "we don't know how". Pretty sure when the 156 cruise control issue first came about Alfa said it wouldn't be possible as well, but someone took the plunge, plugged it in and realised it worked!
Personally if I wanted to find out I'd have the cowl off and look see if any 'spare' plugs were down there hanging around that would suggest you could plug the stalk in. if there is no plug then its a definite no go, however if you've got the spare plug it could be possible.
Other thing to have a look at is whether or not you've got the green cruise control indicator in your instrument cluster.