Yurman wouldn't estimate how long it would take to fully upgrade the radio network or what that would cost, nor would he identify the technology vendors involved in the so-called overlay upgrade initiative. But a spokesman for the NYCT said installing the overlay technology is expected to cost $20 million, an expense that he said should be borne by the NYPD.

But police officials wouldn't comment on which agency is likely to bear the added cost. The $20 million would be on top of the $140 million that the MTA already spent to develop the radio network.

Design work after the merger of the two police departments led to a contract being issued to E.A. Technologies Inc. in Hauppauge, N.Y., and Petrocelli Electric Co. in Long Island City, N.Y., of the radio network, according to the NYCT spokesman. Officials at the two companies couldn't be reached for comment on the radio network, which initially was expected to be finished in 2004 but wasn't completed until the middle of last year.