I mean, i don't know for sure, but i'm pretty sure the people from prison have to volunteer for the work, and i think they're paid a small wage. No way near what the work would normally be paid, but i think there is some consideration.
Edit: I wouldn't assume theres heaps in there for victimless crimes. Don't forget you're talking about quite different legal and political systems, if my assumption that you're in North America is correct.
Fair chance there'll be a whistle-blower or two though so... (refering to David Mcbrides news this week)