Last week I witnessed the cops using a heavy duty saw to revove the lock from a bike that was locked to a parking meter (Bedford Ave, Willaimsburg). They then threw the bike in their police van which already contained several repossesed bikes.
I asked what was going on, they said its illegal to chain yyour bike to anything other than a bike horse (those upside down U shaped things). They said they are removing bikes that are chained to meters and sign posts. They said that if they take your bike you can come down to the station and get it but you have to pay a fine. Plus they dont leave any note or anything so many probably assume their bike has been stolen!
I only saw them do this once; maybe they just did it to make an example (they did it in the busiest part of Williamsburg where everyone could see) there are thousands of bikes chained to illegal poles just in my neighborhood, I continue to chain my bike to the signpost, with the constant fear that it will be repo-ed.