A method and system for selectively allowing uplink wireless transmission from a wireless communication device (WCDs) to a base station without a resource block assignment. Certain resource blocks may be designated for this use but still available for assignment to particular WCDs. When the base station receives data in such a resource block without having assigned the resource block for use by any WCD, the base station may determine based on a class or other identity of the transmitting WCD whether to forward the received data for transmission onto a transport network or rather whether to discard the data. The base station may then act accordingly. This arrangement may help improve performance in a scenario where many WCDs in a coverage area, such as embedded WCDs, would tend to transmit small amounts of data often, but the disclosed arrangement is more generally applicable as well.