hi splib,
this is a great question. as part of the
MaintainIT Project of TechSoup, we've talked to libraries who have paid for one tech person to support multiple libraries. libraries who have been lucky enough to concoct such plans have reaped the benefits in costs--especially small libraries with extra tight budgets.
one librarian with whom i spoke was robin toms of the
Jackson Parish Library in Louisiana. Six libraries shared one consultant; Robin's agreement with the shared tech person was initially 8 hours a month, and has now evolved to paying a flat fee for whatever she needs. she was quite happy with the arrangement, and would likely be happy to share her perspectives.
good luck, splib!
(stories like robin's are gathered in the MaintainIT Project's
free Cookbooks.)