Just as an update for anyone looking to do this, I posted a guide on switching over to skinnier rims and tires here. For switching over to narrower tires on the stock rim, I would definitely look at Schwalbe's tire-rim width guidelines, otherwise you risk blowing out the tires if you use too...
I had to switch out my tires for skinnier ones to get my bike to fit on my local bike racks (Montgomery County MD RideOn and Washington DC Metrobus). Here's a quick guide for anyone looking to do something similar.
1. Find out the maximum width of tires and weight your bus bike racks will...
Here are some useful measurements and nut/bolt sizes for the Lectric XP 2 not mentioned in the manual. Would've saved me a lot of time if I found them online so posting them here in case anyone else is interested:
Wheels
Front and rear spoke hole diameters: 2.6mm
Left and right front hub flange...