Computer copies should not cost to pass on, as the various subs should be working together to give the client the project they want at a resonable price. Every time 1 firm jacks up the price to pass along info it ends up hitting the client in the end. Now if it is cost incurred in making hard copies, I can see that, and we often pass along those fees to those who request the addtional hardcopies. But cad files should not generaal come with a fee when passed along to someone else working on the same project.
Who are you working for? The engineering firm? the Client? the Architect?