jhilden, 
Prompted by the occasional fire scare in a cargo bike group: someone ought to do proper investigative journalism about fire risk from #eBike charging. Found s Swedish report for 2005–2015 with interesting tables, no eBikes (nor mobile phones) identified separately, but at least the phones would seem remarkably safe. No general increase in fire accidents observed!
https://www.elsakerhetsverket.se/globalassets/publikationer/rapporter/delrapport---elsakerhet-i-bostader.pdf#page26