Uh, maybe for those who don't know what time shift on NicoNico is...
There should be a button somewhere at the top that says タイムシフト予約. In order to view something at a different time than when the stream airs, you have to reserve a time shift for that specfic event. Once you do it, you can come back again and view it later, but it will only be up for so long. So yeah, if it airs at some really bad time for you, you can still watch it. You just won't be able to comment or anything... though for what it's worth, you might be able to get on at a time when less people are watching, and not have to get the low quality vid.
As far as whether or not it's region locked, or if you need premium... well, that button shouldn't appear if you can't. I think. There's ways to hide your IP address though.