Yes indeed. A canal path is almost certainly private land and you are there under sufferance, that is not to say they will stop you but if there have been complaints it is better to be above board with those who's responsibility it is to manage the site. Much the same with Railway Stations, it used to be a big no-no in case you caused an injury to anyone or to yourself and maid a claim for compensation. They are fare more relaxed about it now so long as you take care. They do not like tripods though!
This is not to say you can go on or near any of the running lines or works because an injury there can cost thousands in lost running time.