Mikey0124, we sell the Bionx kits here at NYCeWheels (http://www.nycewheels.com
) so we have a good amount of experience with them.
The batteries, like any, are susceptible to extreme temperatures (cold or heat.) In cold temperatures you can expect to get a 25% to 30% decrease in range. At the temperatures you're noting, maybe even half of the normal range. Storing the batteries indoors when not in use of course would help. The batteries are easily removable. You unlock the battery with a key, and it will slide off of its mounting.
We have customers all over the world, including Alaska and Canada, and they all ride their kits without issue. They just know that they will get a decreased range on the colder days and ride accordingly.
While we do ship everywhere, it's nice being able to have a local shop that you can visit with ease. That said, if there's a shop nearby that carries Bionx systems, is friendly and helpful, that knows the product and is able to fully support them, that is an added benefit for you, even if you end up paying a little bit more (there are always cheaper options on the internet, but that doesn't necessarily make them the better options.) Also, sometimes shops don't carry the kits, but are willing to install and work on them (a few of our Canadian customers have arranged such relationships with local shops.) The point is, having an easily accessible contact person is a big plus.
If you opt for a less expensive electric bike kit from another company, just be careful about who you order it from. There are a lot of brands out there. Some are great, others not as much. If you get a kit that requires frequent maintenance and you order it from some guy who has a website but no actual repair shop to back it up, if a problem does arise you might find yourself stuck. This shouldn't be an issue with Bionx though.
Based on your quoted weight I would recommend a 350W Bionx system over a 250W system. The range you're looking to travel should be fine in the pedal assistance mode, which is really the crown jewel of the Bionx system.
All of that said, why do you want an electric bike kit over a pre-built electric bike? It's possible that a pre-built electric bike might better suit your needs and be more affordable.
We created a guide on our website recently to help steer potential customers through this decision. I actually posted a link to it on this forum once before. I'd recommend that you take a look at it, if just to see what you should be considering before you make a purchase: