How important is a brand, or name for a commuter railroad line?...
It is important if one has civic pride; if you don't have much, then it isn't important to you.
As I wrote before, most trains and most railroad companies are/were called by their final destinations.
Texas and Pacific, Missouri Pacific, Missouri - Kansas -Texas, Southern Pacific, St. Louis and Southwestern, St. Louis and San Francisco, Atkinson - Topeka - and Santa Fe, Union Pacific, Northern Pacific, Rock Island, etc.
Would you be happy with Fort Worth Rail, Fort Worth Railroad, Fort Worth Line, etc? Keep in mind that there is a railroad company already called the Fort Worth and Western Railroad which FWTA hopes to extend the TexRail trains onto in the future. How about the Grapevine Rail, Grapevine Railroad, Grapevine Line, etc? Keep in mind that there is a railroad company already called the Grapevine Vintage Railroad which will share the TexRail tracks as far as Tower 60.
How about nicknames? How about the Cow Town train? How about the Fat Show train?
How about stealing another city's slogan? The Spirit of Fort Worth? Pride of Fort Worth?
How about the major river? The Trinity River Dinky, because Express is already in use?
Why don't you suggest another name showing civic pride, maybe it will catch on?