Absolutely. Its not recommended! But you can absolutely do that. Disk based raid groups are the bane of EVA and Clariions and doing away with disk based raid groups is a core technology of 3PAR, Compellent and XIV.
To split that up and isolate spindles by CPG has several areas of concern that can "get you". I highly suggest you engage your Sales Engineer to help you make sure its done perfectly. Here are some notes and concerns, use at your own risk
When you run through the CPG creation/edit wizard you will see the filter gui that makes the selection of what disks/cages can/can't be used. Filter the old and new CPGs per your requirements. Your old CPG may have already written data to your new drives. You can us Dynamic Optimizer to move that data off.
Concern 1: Freespace reporting and monitoring. You will need to figure out a way to monitor how much freespace is left available to each CPG, since not ALL of the reported system freespace is availabe to each CPG. Your old cpg/disks could be full, but there could be TBs of free space reported by your new shelves.
Concern 2: Understand how your CPGs and disks are balanced between node pairs. F400, I assume you have 2 node pairs (funny way of saying 4 nodes). For example the 4 new shelves *should* have been placed 2 on nodes 0 and 1, and the other 2 shelves placed on nodes 2 and 3. That default physical setup will have the multiple departments sharing the 4 nodes, if absolute separation is desired, with 4 nodes, you could create CPGs that would isolate workloads to one node pair or the other.
Concern 3: CPGs are highly customizable/configurable, and you can easily paint yourself into a corner if not planned or executed properly. Proceed with caution and HP assistance if you can't redirect the business to stick with defaults
Hope that helps!
--Richard