Local TV Networks are usually tied into the large Jingle Companies.
Like I said they package it up with their sales.

It doesn't hurt to ask.
Try the Advertising sales department.
Usually They will tell you how jingles are packaged with ad time slots..

The same with Local Radio Stations
ask the Ad Sales Department.

You'll probably find that they don't use local Studios for Jingles unless you are near a big city.