HSDPA is a common channel and as a result CEs are shared among users. essentially, users are multiplexed on a TTI (= 2ms) basis, and as a result the same resources (i.e. CEs) can be shared by everybody
on the other hand, HSUPA is a dedicated channel which also makes use of soft handover. This situation is similar to R99 channels: CEs must be allocated on a dedicated basis for the duration of the HSUPA session, and of course different resources are required on each Node-B participating in the HSUPA active set.
hope this helps