It varies from state to state, county to county and district to district.
You will get some districts which help one another quite closely, but this is also a model that operates at county level too. You will get counties working on shared services within their local government. One might take on all the roads stuff, another the HR and pay, another the IT and another does all the education planning / strategy.
Some elements of the BSF model are taken directly from the district model in the US, namely a single manager / team leader / director over many schools, a standard infrastructure, centrally hosted services (remember the SIF model comes from the use of information at district level) and shared resources.
But ... as already pointed out ... it can vary wildly.
And as it seems not just in America but here in England that trying to centralise education over a WAN really doesn't work that well as has been reported by our IT cousins across the pond. Cost cutting politics seems to be the order of the day and we who are left after all the school internal jobs have been cut are left to cope with an ever increasing workload which really is false economy in real term service.
From reading some of the posts on here from the guys in America it seems they have a real job getting finance as well as getting jobs done within a week, that would just not do in our school. When job is logged through the helpdesk on average it is less than 1 minute for a response through the helpdesk to the end user and the job is usually on average undertaken in just less than 5 mins with average total fix time of 14 mins. This is for a medium secondary school with 720 students and teaching and admin staff with external entities joining the 1000 plus end users that we support with 350 desktops and approx 100 laptops, this is supported by 2 full-time and 1 part time IT staff.
I know this is in no way the size of some of our American friends campus's but students and staff need to be able to rely on a system which works well 24/7 365 and only supporting this through proper finance and strategies not centralisation which will in the long run end up costing 2 - 3 times as much, as the equipment which is part of the MSU's procurement package is usually 2 - 3 times as much to buy and usually of inferior quality with smaller warranties.
Big is not always beautiful.
Our La has failed 3 times to get one of our BSF schools to work over VDI using Citrix virtual desktops and yet they still continue to throw good money and time trying to get it working. The theory in principle is great but in real terms it is just a business model which for education will not work as the needs of education are so much more demanding than business overall.
Its a case of the inmates have taken over the asylum so god help us all. ;)