Comment by accrual
4 days ago
I also know of a company who does this. The reason in their case is they act as a network concentrator, bridging hundreds of client IP spaces, so this helps them avoid conflicts with their own space without having to NAT constantly. There is still a lot of NAT for the more common ranges.
If they converted to IPv6, they could easily have a globally unique address space. Real globally unique, not probabilistic.
The fact that the network concentrator co uses DoD v4 address space to avoid conflicts implies that their clients are bringing v4 addresses, so IPv6 is utterly irrelevant in this situation.
It's common for a network to address its own devices with v6 while carrying v4 traffic either natively or by tunneling. Saves v4 space.