As i know 50 resource blocks are available for every Transmission Travel Time (TTI) i.e. 1 ms. So in one millisecond if E-NodeB has resources and each UE has 1 RB, it can maximum serve 50 UE's in one TTI.
Theoretically it is the possible but in practical aspects it is very difficult to serve 50 users in one subframe/TTI. To find out this much excellent scheduler is hard.
I feel the limitation of UE also depends upon (Physical Downlink Control Channel) PDCCH capacity. If this channel has enough Control Elements (CCE) and radio bearers are available, E-nodeB can handle those many UE's in one TTI.