Catalyzes the phosphorolysis of cellobiose, yielding glucose 1-phosphate and glucose. Is inactive against cellotriose and the disaccharides lactose, chitobiose and xylobiose. May be the primary enzyme for processing cellobiose in T.neapolitana. D-cellobiose + phosphate = alpha-D-glucose 1-phosphate + D-glucose kcat is 26.3 sec(-1). Optimum pH is 4.5 to 6.0. Optimum temperature is 85 degrees Celsius. Glycan metabolism; cellulose degradation. Glycan metabolism; beta-D-glucan degradation. Belongs to the glycosyl hydrolase 94 family.