If they didn't count it against their caps, could you imagine all the slamming they would get for favoring their own service but not others? Net Neutral.
Then don't have the caps if you are going to sell products competing in the marketplace that is going to suck huge amounts of data. Double dipping as a business practice is not exactly ethical either and that is what Concast is looking to do.
They are not charging you for going over the 250 so not sure where you are getting this double dipping stuff.
No, they just boot you off. Which of course means you have either find another provider or go without, finding another provider can lead to increased costs.. maybe cheaper but doubtful.