Oh... we've looked plenty hard. I can safely say I don't know of a single rail in this city that hasn't already been hit by at least 10 other film crews. Last year we hit about 20 of them, which happened to be 20 of the most played. It's just fun to find rails that no one else has slid, or that people aren't familiar with.
So, it's not that we don't know where they are... it's that they're all so played and we've already spent an entire season on them, that it's just whack to hit them all over again.