I think you have to play with Outbound route plans both side. Maybe Dial patterns wizards can be help you.
Like a ready paid module i can suggest you to look ClassOfService (CoS)… Its a good module but your case i think you don’t needed. ( just idea. )
My guess is that you have the context for the trunk set to something like from-pstn, when, for a tie trunk (intra company trunk), like this, it needs to be from-internal.