If there aren't enough beds in ICE detention centers, and they can't get anyone else to hold them, one of two things will happen. They'll be released with a summons to appear at a date certain, or lesser offenders will be released to make room.
Waves of new enforcement programs with names like Operation Community Shield, Operation Predator, and Operation Tarmac produced a record 161,676 deportations nationwide last year, a surge of 60 percent since 2000, and a similarly large increase also has occurred in New York City.
http://www.boston.com/news/nation/articles/2005/08/14/deportation_surge_leaves_void_in_brooklyns_little_pakistan/
(It's a start...)