I looked around, and didn't find a whole lot of resources on the subject. However, I did find the following two pages:
http://web.grps.k12.mi.us/sped/home-school.html
In order to qualify for services, the home school must be registered with the State of Michigan, Non-Public School Liaison Office, (517) 373-0796.
http://www.hslda.org/hs/state/mi/200601200.asp
The family decided to enroll him in public school during the 2004-05 school year in order to get additional special-needs services. (emphasis mine)
It seems Michigan does require that you be enrolled to make use of special needs services. Sadly, the wording on the Individuals with Disabilities Education Act doesn't specifically provide for homeschools, so it's left up to the states how to interpret it. In the case of Michigan, apparently not favorably. I could be wrong of course, and you should probably contact your local and/or state homeschool groups for a final answer:
http://www.home-school.com/groups/MI.html
-Ted