There is a problem in our environment granting a non-DBA account sysadmin privilege. We can, if absolutely necessary, temporarily grant it for installation, but have a much harder time granting it permanently. That is why I need to know if FIM accounts need SysAdmin privs in SQL Server for installation and not normal operation? Where can I find documentation specifying necessary account permissions?

You should only need this for the install for both the sync engine and the FIM service, since both of those procedures will create or modify DBs in SQL. After install, it shouldn't be necessary for the installing account to be an SA in SQL. One thing to add: I know that with ILM 2007, SA in SQL was necessary for updates, since some updates modified the SQL schema. I would think that requirement still exists now for FIM, as well. I thought I heard that this won't be necessary in future build but am not sure.