An improved arrangement is described for signaling enhanced capabilities of a wireless data communication system to a dual-mode wireless handset seeking access to such capabilities and normally operating in a first (non-enhanced) mode. The arrangement, which is especially advantageous for ascertaining operating mode capabilities of a new cellsite to which the handset is being handed off from an existing cellsite, includes a separate capabilities server that is associated with the system and contains a data base populated with information indicative of such capabilities. The handset generates a suitable query message which is transmitted to the data base in the first mode after the handoff to retrieve the capability information for the new cellsite location. The handset is switched from the first mode to the second (enhanced) mode for post-handoff operation if the retrieved capability information indicates that the new cellsite is capable of operation in the enhanced mode.