Hydrolyzes a wide variety of P-beta-glucosides including cellobiose-6P, salicin-6P, arbutin-6P, gentiobiose-6P, methyl-beta-glucoside-6P and p-nitrophenyl-beta-D-glucopyranoside-6P. Is also able to hydrolyze phospho-N,N'-diacetylchitobiose. 6-phospho-beta-D-glucosyl-(1->4)-D-glucose + H2O = D-glucose + D-glucose 6-phosphate Divalent metal ion. Manganese, cobalt and nickel ions enhance activity whereas magnesium, calcium, strontium and zinc ions do not. Homotetramer. By N,N'-diacetylchitobiose. Belongs to the glycosyl hydrolase 4 family. Was originally (PubMed:2179047) characterized as part of a cryptic cel operon for a cellobiose degradation system. The Cel+ phenotype is due to mutations making expression chitobiose-independent and altering the substrate specificity.