Methods and apparatus are disclosed to facilitate wireless communications between a wireless transmit receive unit (WTRU), legacy base stations and base stations using different operating parameters, such as evolved high speed packet access (HSPA) systems Third Generation Partnership Project ((3GPP) Release 7, Release 8 and beyond). Preferred WTRUs are configured with a medium access control (MAC) sub-layer component having a subcomponent with HARQ buffers, such as a subcomponent configured to provide MAC-es and MAC-e functionality and/or MAC-is and MACi functionality that include hybrid automatic repeat request (HARQ) processes, some of which are preferably operable with enhanced dedicated transport channels (E-DCH). The WTRUs are preferably configured such that they reconfigure their MAC subcomponents during soft handover while minimizing induced latency and data losses associated with HARQ processes. In some embodiments, the WTRUs are configured to prevent flushing of HARQ process buffers in soft handover scenarios with a Node B that does not support UL enhancements, e.g. higher order modulation (HOM). In other embodiments, flushing of HARQ processes is used but amelioration of adverse effects is addressed.