I can verify that Xteve can be added as a source to Channels DVR. Though without guide data, it's not useful to do so, in my opinion.
Yes, IPTV providers streaming US channels are definitely skirting laws, though elsewhere in the world, the situation may be very different, both from a commercial and legal perspective.
Though with Hollywood insisting on licensing content by geography, the situation where you're watching content from a different country than you're residing in is definitely a (dark) grey area.
It's been quite possible to watch TV stations from adjoining countries in Europe for decades using a normal TV antenna. I assume the same is true for folks living close to the Canadian border. Viewing 'cross border' content is not something new, though streaming has effectively erased the geographical limitations. Just ask Netflix...