A communication system reduces set up time for an inter-technology handoff of a multi-mode mobile station (MS) from a source network associated with a first radio frequency (RF) technology to a target network associated with a second RF technology by pre-establishing, prior to a determination to handoff the MS, a registration state of the MS and an authentication of the MS in association with the target network and second RF technology. In order to pre-establish the registration state and authentication, the MS exchanges messaging of the second RF technology with the second network via the first network and first RF technology. To facilitate the exchange, the MS includes shims in a second protocol stack associated with the second technology, which shims intercept second protocol stack signaling and redirect the intercepted signaling to a first protocol stack of the MS, associated with the first technology, for tunneling to the source network.