I'm not sure how much these trials will prove. Surely a lot of the potential use will be privately owned ones that people use for a short-ish commute or run to the shops etc. The market for pick-up-and-go rental could be quite limited, and will only really apply in large towns & cities, for people who have perhaps driven in and then need to go a mile or two to other locations, as an alternative to a taxi or bus. The trial will give little evidence for overall demand and practicalities.
And for those complaining that they can be left to litter the streets? Easy, if one's been abandoned on the pavement, chuck it over a fence or in the canal.