Development of Creative Commons licenses

[Erik Moeller <erik_moeller AT gmx.de>]

Hi,

CC-BY-SA-2.5 Generic specifies, in 4.b, that one may distribute a work
under any of the iCommons equivalents of the license.

Let's say I have a page in a wiki that I offer under CC-BY-SA-2.5.
Someone takes that page, and redistributes it under CC-BY-SA-2.5 England
& Wales, citing 4.b.

Someone then makes a modification of the "England & Wales" licensed
version.

Can I then only use this derivative work under the terms of England &
Wales? While CC-BY-SA-2.5 has an "any equivalent international license"
clause, I could not find an "any equivalent generic license" clause in
the international licenses.

If this is the case, doesn't that seriously impede the share-alike
process? E.g., if I have a wiki licensed under CC-BY-SA-2.5, and someone
creates a fork under an international variant, I could then only make
use of their modified versions if I switched my own wiki to the
international variant. I might then end up in an incompatibility dead
end.

Can someone explain to me the two-way interaction between generic and
local licenses? Is this maybe something that should be in the FAQ?

Best,

Erik