Mike,
Your points sound good, but I'm just a Grapevine resident, not someone 'in charge'.
While it seems a bid odd to build an entire railroad just because someone gave you a lokie, it does seem to fit into the overall development plan for Grapevine. It's probably a case of "opportunity knocked".
I just like knowing that there is a narrow gauge steamer a couple minutes from my house. It's not on public display, but you can get in to see it if you know how.
Cheers,
Michael