Yeah, FiOS offers that from time to time, usually for about a week. We don't bother with it because we're already getting most of those channels.
We might downgrade to basic service though, so I suppose when that happens I'll take advantage of the free previews.

Yes i have gotten 9 months of HBO free for the cable company i have sucks and I constantly have to complain about something and so i always talk them into giving me free premium shows. I call to cancel every 3 months and they always say well would you like 3 more months. Of course the answer is yes though I rarely ever watch them!