You have to ask who the volunteers are likely to be.The unemployed who can only do a max of 15 hours a week or risk there money being stopped,the Retired,and the imprisoned. Then you can add enthusiasts that can do stints every now and again/regular weekends.In this they will be competing with other calls for volunteers.
I really do not mind the idea of volunteering in principal but it would i think be annoying to know that your work was going to keep the less than competent well/over payed in there job,it would still annoy even if they were doing a good job.Perhaps the restoration groups will then have to run the canals afterwards with toll houses at the junction with the BW waters and collecting mooring fees,maybe even having a boatyard to generate it's income.
The towpaths could be maintained by the fishing, cycling and rambling organizations.LOL Then again maybe not