[lir-wg] Reserved addresses

This may not be the best list for posting this question in, but I've been
unable to figure out which one to use instead. Please forgive me.

In a current project a number of addresses is needed for closed IP 
communication between a number of institutions. The logical choice for
this is some RFC1918-space, but certain people fear that no matter what
1918-addresses we may choose they may be in use internally in the involved
networks and thus unavailable to this project.

My knee-jerk response as a somewhat conscientious networker is "So what? 
We'll just have to pick some addresses not presently in use. There should
be plenty. Yes, it will take coordination, but that's life."

Someone else, however, picked up on the fact that there's a large number
of addresses just marked "reserved" by IANA, and they probably are not in
use, so why don't we just grab e.g. 82.0.0.0/8?

I really want to avoid this and stay within the RFC1918-nets, but I need
a good response. 

Could someone explain to me what the nets marked "reserved" in for example
http://kmserv.com/testbed/ip-space.txt are expected to be used for? Special
stuff or RIR address space?

Peter B. Juul, 
Uni·C (PBJ255-RIPE)