dd from the control station won't give you much. The problem is that you need access to the raw disk devices (data LUNs) themselves - the CS won't really give you that. What you're looking for is a method to access the data LUNs themselves.
Your best bet would be to approach this from the fabric. You need to connect another server to the SAN fabric and access the LUNs on the CX array behind the NS20. From there, you could attempt to copy the block data with DD. The other problem is, the filesystem used by the Celerra is UXFS. You'll want to tinker with the right Linux build to install the drivers, then see if you access the LUNs and run a DD to get whatever you can from the disk.
Not knowing your situation, you might be better off paying a data recovery service to try and fetch the data for you, assuming EMC Support has quoted a bill that's too large.
I dont think you will be able to find drivers that understand the uxfs file system.
Your best chance for recovery is to work with EMC support using the EMC tools