I would imagine some brokers push in house lenders, title companies, etc., and some do not.
In my company we have both an in house mortgage and title company; our brokers do not 'push' us to use them at all but they do make sure we know they're there.
I very rarely use them; typically a customer or client will see their office in our lobby and either ask me about them or just wander in. They do a good job, just not the ones I'm familiar and most comfortable with.