According to james.cutler@consultant.com <james.cutler@consultant.com>:
which, in general, requires provider change and renumbering of globally unique addresses, unless you own /24.
Moot since we are not discussing office moves. However, renumbering to global IPv6 addressing allows easy coexistence with the global Internet
Alternatively, if you have network addresses that you want to be sure don't leak to the global Internet, ULAs work well, too. If you pay attention to RFC 4193 and select your Global ID randomly, when you merge two networks there is no meaningful chance that the ULAs will overlap. -- Regards, John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. https://jl.ly