I suspect that they'll have to allow publishers to opt out if they wish to, in the same way that Instapaper does: http://www.instapaper.com/publishers
I don't think it likely that many publishers will opt out, though. They'll still get ad impressions for the initial page load in addition to the kickback for the visitor's readability click.
I didn't read that as 'the company will pay them even if they explicitly don't want to be paid'. I read it as, 'the company will attempt to make contact and pay them even if they haven't yet signed up.'
Isn't this just begging to get sued by some publisher who really doesn't want to participate? IANAL, but it seems like they'd have a decent case.