[Arkcon]

Hmmm...question is kinda strange to me. But I'll bite.

Yes, there are 2 sides to a warp point, one in each system.

If you mine just one side, the enemy fleet can park on the other side indefinitely. They only get hit when the 'Warp' order is given, and they appear on the other side.

That said, I think most people pretty much just mine 'their' side (if applicable) of a warp point. Mining both sides is kind of overkill. For various reasons.