E-Joe has a folding capability but yeah, it's not for rolling around at all. I've folded it into the bus when it was snowing a lot outside, etc, and needing to take a bus. When folded, it does the job of being smaller, but the size isn't super compact to my taste.
Also note that if you are driving 10 miles one way from your home to the train station, that's 20 miles total.
EJoe Epik SE's battery will be able to barely fit that range, initially, but battery gets weaker over time, too.
So you might see the bike not being able to handle that distance over time in 3 - 6 months.
If both portability (like rolling the bike in the city) and range are important, have you seen or considered these below yet?
http://electricbikereview.com/tern/link-d8-with-bionx/
http://electricbikereview.com/tern/node-d8-with-bionx/
They are around $2700, and above twice as much as EJoe, so that's the downside indeed, but I think these will do a job for you. There are also other choices like electric brompton, and it's compact, but you will probably need that power from a motor / battery combo like bionx to handle your commute. BionX is a much more tested system, too.
And around metro DC area, it still snows in the winter, so tern node's 24 inch tires would be preferred in these weather conditions, compared to tern link's 20 inch. But that's assuming that 24 inch isn't a problem for bringing into the train.
Let me know what you thought of my opinion.
This is a comment coming from an EJoe owner.