It should be possible to make a little application that can do this for us. Fetch some samples of the login sequence with the firefox extension Live HTTP Headers and/or something else, then write an application using e.g. libcurl, add something which lets you configure it on a per-network basis, add something else that automatically runs the application on a per-network basis (and the post you linked to could help), and you're done.

Now the minor part: Write the application!