A power transmission belt incorporating an adhesive treatment system and method for bonding fiber to rubber which includes an optional primer coat based on a low-molecular-weight isocyanate, followed by an overcoat including: (a) a prepolymer based on an isocyanate-terminated diene oligomer, and optionally (b) a low-molecular-weight isocyanate, and/or (c) a thermoplastic urethane comprising the reaction product of the same prepolymer with MDI and EHD. A polyester, aramid, or carbon fiber tensile cord for rubber reinforcement may be treated with the primer coat and the overcoat. A power transmission belt or other dynamic rubber product having ethylene-alpha-olefin elastomer as the primary rubber constituent may be reinforced by the tensile cord.