There are a lot of different kinds of plans. Strategic Plans are usually about how to evolve and grow an organization and where it intends to focus its efforts. This is clearly important for any non-profit, but I am not sure (and I could be mistaken here) if this is the right kind of plan for addressing the historical integrity of the railroad.
The National Park Service has established a regime of standards and practices for the preservation of just about anything. I would expect that some of these things have already been done for the C&TS, but I am not familiar with the work that the Friends and Commission have done.
Following the NPS model for preservation planning; a historic structures report would survey the site's historic structures, analyze the historical significance of the site and structures, examine the integrity of the site resources, and finally propose a resource treatment plan. The treatment plan would aim to restore, rehabilitate, preserve, and/or reconstruct the site's resources to reflect their condition during a specific period of historical significance that would be determined based upon the findings of the earlier report components.
A treatment plan is like a master plan specifically created to preserve historic resources.
A strategic plan would address organizational issues necessary to achieve the preservation goals of the treatment plan.