I think it's more along the line of they got stuck with it than going along, as the clusterfuck was already in place when the current IT department started working here. I'm guessing they were planning on moving to Sharepoint compatible system (Lotus Notes was already in use before Sharepoint), but ran out of money to do so along they way due to budget reduction & tuition freeze.
Either way, it's a huge pain. I also hate that I have to manually input the calendar items on to my iPhone if I want to access them outside of work.