Does Sewage Ejector system need a dedicated circuit?
It all depends on several things. 

What size is the circuit?
What else is one it?
What do the manufacturer's instructions say?

Typically you'd only need a dedicated circuit for something like this if it is big enough to warrant it, or if the mfg requires it. 

When I say big enough I mean 50% of the circuit size since you are combining a fixed in place appliance (the pump) with general use items.