Different states have different amounts of time a person can be held in another county without being transported to the county where the warrant was filed.
In Texas there is a ten day rule. If the county that put the warrant out there doesn't pick the individual up within ten days the person is released from jail here in Texas.
Other jurisdictions have different ways they work with this so you should hire an attorney to help this individual out.
Platten Law Office
304 West Rusk
Tyler, Texas 75701