We would calculate IDC on the amount it cost the college to
operate the program, whether that source is the sponsor or
some other entity.  Each collaborator would compute its share
some other entity.  Each collaborator would compute its indirect costs
in the same manner.

Of course a common way of showing cost-sharing (which our office
discourages strongly but usually, alas, without result) is to
to compute the indirect cost on the shared amount and then show that
as part of the sharing.

Peter J. Dolce
Director, Research Support Services
Meharry Medical College
P 615 327 6703
F 615 327 6738
xxxxxx@ccvax.mmc.edu