With a heavy enough filter, you can completely remove moving lights and objects like cars and people while keeping stationary subjects and lights exposed properly.
compuwar do you have any examples floating around in your library because I'm very interested in the outcome using a filter as you suggested? I only have a Digital Multi-Coated UV Filter and have wanted to buy a few different filters for such photos around my area. Maybe it's just me but certain signs at night taken properly just look really cool.
Good luck to the OP and if you can please post some of your final photos when you get the chance.