actually you can explore it becuase in the gameplay videos they say u can switch between multiplayer,campaign, and other game modes u can walk through maps also so yes it is like borderlands
No it isn't like Borderlands. Borderlands has gigantic open areas linked by teleporters. BRINK has smallish, arena-style maps that aren't linked by anything. And good luck walking around because there will be highly competent AI trying to gun you down whether you're playing multi-player, challenge mode, or single-player.
@jakovasaur: Don't worry about the game getting old. The developers have stated many times that the maps are full of "deep context" items, things that help reveal the story of BRINK that are just lying around the battlefield. Between looking for these secrets, maxing out your characters, creating your dream soldier, and mastering the S.M.A.R.T. system there will be plenty for you to do.