Wikipedia refers to "ex-railway locomotives", but this could easily be a poor translation of a modified railway locomotive design.They look very odd. Single ended, fixed to the gate, the link connecting them spanning the waterway, and running on pneumatic tyres on a concrete surface. I wonder if they were built specially?
The lift has now been given the visitor experience and dazzle camouflage treatment.
See https://simonszand.net/Pente d eau Montech.html
A Google translation of the webpage gives some strange results, e.g. "boat swallowing".