I believe the SP18 group has rail and ties (from the scrapped Jawbone) and some of the original right of way as part of their long range plan. However, as with almost any non-profit they need more volunteers and funding.
Do remember that the C&C purposely avoided the towns along the west side of the valley, concentrating instead on the east side of the valley closer to the expected mineral customers as well as avoiding the numerous streams coming out of the Sierras.
Other than at Laws, most other locations along the original right of way in the valley are pretty isolated. And if you build track, how to you attract enough visitors to justify the effort?