Voluntary TPR - how does that work?

We were told today the CPS is actively talking with T's BP to get them to voluntarily surrender their rights (is that the right way to say that?). We were very surprised initially but on the other hand it sorta makes sense. The kids have only been in care since end of June but the reasons for removal will very likely result in criminal charges against a number of family members (including BP) as well as TPR sooner than later anyway. DH would rather they all went to prison, but pragmatically it would be better to get the kids permanacy now rather than drag it out, I'd guess. How does voluntary surrender usually work? Anecdotally do many parents in this type of scenario agree? Do the BP usually get to specify any "conditions"? Thanks for any insight!!~ Debra