Wearing my researcher hat, the answer depends on what sort of research
you're trying to conduct. There are more things to do with a fiber
than just running IPv4 over it.
--Steve Bellovin, http://www.research.att.com/~smb
yes, ipv6! 
Actually, some of the research networks seem to be places to
test/eval new hardware, software, techniques and/or pass large datasets
from lab to lab in larger collaborative projects. Often the
faster/newer/sexier gear had been tested on these 'test' networks prior to
deployments in the field.
Steve is right though, it's not all ipv4 on the links...