A mobile device can be assigned to an extension configured as a Queue Agent (“QA”) in a call-queuing enabled virtual private branch exchange (vPBX). This and other mobile or fixed devices can be interconnected to form a virtual call center. Each extension can be assigned various rules, which specify how the incoming calls are answered at the extension and how calls in the call queue are selected for answering by the QA. As part of the rules, the vPBX system forwards calls from a call queue to the QA based on QA's availability status. If a location-aware mobile device is associated with the QA, the vPBX system can determine the QA's availability status based on a geographic location of the mobile device. A most geographically proximate agent can be selected for answering the call.