How about creating /e8f6b078-0f35-11de-85c5-efc5ef23aa1f/aupm/notify.do on your server to notify Comcast users about what their internet service provider is doing? If people started doing that en masse it could bring attention to the problem and with enough publicity get Comcast to reconsider JS injection.
I don't really understand the point of this, either. Couldn't they starting redirecting users to a static page somewhere if there were a real need for a "critical and time sensitive" alert? If the supposed alerts aren't critical enough to justify doing that, use email, IM, RSS or twitter, or even build a custom notification notification app.