Yes, very common and done throughout travel softball.
Yes, it is becoming more and more common in college since the mound was moved to 43 feet and that hitters and equipment continue to catch up / surpass pitchers dominance. In conference, Syracuse used a closer role all year. UNC had a school record for saves this year. Even FSU mixed their pitchers quite often in the same games (as did OK and UF in championship series as well).