All non-motorized uses are allowed. In the winter snowmobiles also use the trail (and it is groomed by the local snowmobile clubs). Signs posted at trail entrances summarize the allowed uses and expectations. ATVs and other motorized recreation are not allowed on the trail.
I believe that all Vermont Rail Trails are at least Class 1 friendly. I saw Class 2 bikes on the Island Line Rail Trail. I don’t think that there are any Ebike issues. I assume that the 15 mph limit would apply.