A transfer can go either way, and the reason behind it tells you almost everything about whether it is good news or bad.
Inmates get moved for two broad reasons. The first is as a reward for good behavior and program completion. When someone earns a lower custody designation, the system moves them to a facility that matches that lower security level. That kind of transfer means easier daily life, more privileges, more freedom of movement, and generally a calmer environment. If your boyfriend has been keeping his record clean and doing what is expected of him, this may well be that kind of move.
The second reason is disciplinary. When an inmate creates problems at a facility, gets involved in incidents, or poses a management challenge, the response is often a transfer to a more restrictive environment. That kind of move comes with fewer privileges and a harder daily experience.
The communication gap you are experiencing is normal regardless of the reason. Transfers create a blackout period while the inmate goes through intake and processing at the new facility. Phone access does not come back until he is assigned housing, cleared by staff, and has his approved call list set up. That process usually takes anywhere from a few days to a couple of weeks.
The most direct way to get clarity on why the transfer happened is to call Southwestern Correctional Center and ask to speak with his counselor once he is processed in. In the meantime a letter through InmateAid sent to the new facility lets him know you are aware of the move and waiting to hear from him.