Fixed size VHD and VNX Thin provisioning question?

For Windows 2008 Hyper-V a fixed sized VHD will have all of its capacity zeroed, so all of the space representing the size of the VHD could be claimed.  However, if the VNX has zero reclamation facilities, that space could technically be reclaimed.  For example, if a LUN migration with zero detection was performed, the contiguous zeros written to the fixed VHD could be reclaimed.  Also, if compression is enabled for the LUN, there may be less space taken than would otherwise be represented by the fixed sized vhd.