Whether its on his record or not, the new employer cannot change his employment status unless he has deliberately witheld this information in the past.
If a CRB check was not necessary for his post in the past, then it should not be necessary now. His role has not changed and he will be protected under TUPE when being transfered to the new employer.
Tell him not to let it scare him, it sounds like a very general statement. As you say "something about criminal records" but nothing specific or anything that will apply to him I'm sure.