I'm not sure what you mean by "low-risk" prisons. Do you mean "low-security?" That's mysterious, considering that the judge wouldn't allow them out of prison while their cases are appealed, on the grounds that they are "flight risks."
Incredibly enough the judge said they would be flight risks to go to Mexico. The term may well have been low security rather than low risk. Apparently prisons with cells are primarily for high risk offenders.
Flight risks? Source, please.
I've read the judge's Orders denying the agents' motions to remain free on bond until Appeal. It says no such thing.