Currently, the city of Austin is working to negotiate ownership of the trestle, and until (ownership is established) it's not really appropriate to move forward with a bunch of alternatives for designing and rehabilitating this asset when it's not 100 percent clear that the city has complete ownership.
If it were to go ahead, a loan would helpfully sidestep the issue of ownership, as while museums can't usually dispose of items, the 2022 Charities Act allows such disposals where there is a moral obligation to do so.