Hannover: Hapagfly/HapagLLoyd Express (or HLX), probably Air Berlin. Dont know if Cityline still has a base there.
Dusseldorf: well, LTU of course, dba, dunno about the others.
Bremen: OLT, probably still a small Contaict Air base, dunno about Cityline.
Munster/Osnabruck: no idea, sorry, except Air Berlin probably since they seem to have a crewbase at every tree along anything that remotely resembles a runway.