In THEORY, once an address range is delegated to you it is YOURS. CIDR
permits "holes", that is, more-specific routes.
Some providers try to force you to "give back" the address(es) when you
leave. MCSNet, and most others, do not. My view on this is that once you
receive an address consisting of at least a Class "C" block (ie: the last
octet is yours) then it is yours to keep -- period.
For sub-C allocations there is no good way to delegate those, and as such
at present we view sub-C allocations as belonging to us, and I suspect most
other providers who are as aggressive as we are in delegating small pieces
of address space also view things in this fashion.
Looks like a double standard to me... The same argument could be placed
for any subnet not on an 8,16, or 24 bit bound.
Remember that consistant policy is a "Good Thing"(tm?) and something that
works, -across the board- will last us longer than some simple haq that deals
w/ current, broken hardware/software. (Will this policy work in 24 months?)