Contemporary theoretical considerations of glass transitions in miscible binary polymer blends give the thermodynamic functions associated with the excess properties of mixing in liquid and glass states. A striking feature of the present analysis is that fewer assumptions are involved in the derivations. The values of the new parameters are reported for a number of polymer pairs, representing various types of intermolecular interactions. It is demonstrated that the enthalpy and entropy of mixing are virtually discontinuous at the glass transition temperature of the blend, T-gb, particularly for the cases of large deviations of T-gb from the weight-average values. In addition, the difference between the polymer-polymer interaction parameters of the blend in the liquid and glassy states, Delta chi, is indeed linearly related to the reciprocal of T-gb. Other implications of the results are discussed.