My post was lost. 
So here is the short version!
I have a VNX5200 block only, no control station. I'm pretty new at this so I take no responsibility for any damage you may do to your LUN's!
I figured out how to present LUN's as read only to my Veeam windows host.
To do it I created a second storage group and added my windows host to that storage group. I called that storage group Veeam.
Using the navisphere cli issue the following command.
naviseccli -h <SP_IP> storagegroup -addhlu -gname <storage_group_name> -hlu <host_lun_SCSIID> -alu <CX_lun_ID> -readonly
My command looked like this.
naviseccli -h 10.0.6.50 storagegroup -addhlu -gname Veeam -hlu 8 -alu 1 -readonly
I started off with test LUN's, and test vm's.
After you issue the command rescan the storage on the windows host and rescan the proxy in veeam. I put my veeam proxy into SAN mode and backed up the test VM. It worked!
I also cannot initialize, delete or do anything with the volumes in windows. They truly are read only.
I went ahead and tried this with some of my tier 3 lun's/vm's and it worked. I ran a veeam backup job against a VM that was not presented to the storage group and it failed, as expected, since the proxy was in SAN only mode.
I have not tried this with any tier 2 or tier 1 servers yet because I was hoping someone could chime in on this because the -readonly switch isn't really documented anywhere.
Thanks!