No - that is not supported. Ability to manage multiple clusters with a single XMS came with version 4.0. A cluster running version 3.0.x (or earlier) cannot be managed in that fashion - they need to be managed by their own XMS.
I couldn't find any restrictions for the multiple cluster support for XMS version 4.0.
Can you manage an XtremIO cluster running version 3.0 and an XtremIO cluster 
running version 4.0 with an XMS appliance running version 4.0?