Winter travel to Interlaken and into the Berner Oberland region?

Those towns are completely accessible by train. I was actually there mid January two years ago. Interlaken in nice while the smaller towns actually in the mountains are AMAZING! Murren and Wengen were nice for walking around. Lauterbrunnen is great, too.

They are major ski resorts. Thousands will be there in January having the time of their lives.
If they get a lot of snow on the tracks, they they just pull out one of these.
https://www.youtube.com/watch?v=oGndpEPgEgw

You should be aware that over 20,000 people show up for the World
Cup ski races in Wengen. Next year they will be on January 18-20.

http://www.lauberhorn.ch/en/home

Sam, I would LOVE one of those things for my driveway!!! Sweet.

There are residents who actually live there...in Lauterbrunnen, Wengen, Murren. It's not a town that closes when the tourists go home. Hardly!

To repeat, these are real towns where real people live, and need transport 365 days of the year.
The Swiss public transport system exists primarily to transport locals about their daily business. Tourists are a minority of the passengers.
The mountain locations have two seasons, the bigger one in the winter and a smaller one in the summer. Spring and Autumn are the "off" seasons. In winter some high mountain roads are closed, but the trains still run and some places are only accessable by train (Mürren, Wengen, Zermatt etc.)

Thank you all for the fantastic insights and ideas.

I'm glad to hear everything is still functional for visitors in the winter and that Switzerland has such a robust transportation network. I'm originally from the Pacific Northwest where some towns in the mountains essentially shut down or are not walk-able in the winter.

Not only is it walkable, there a tradition of winter wandern where the trails are groomed and without any special gear one can hike. Bring good winter shoes, i.e., Gortex.

We had a blast in December 2017. It was snowing like crazy and the snow was so deep our sleds were getting buried on our way down from Almendhubel to Murren. However the path from Murren down to Gimmelwald was superb and we did that trek 2 or 3 times...can't remember. It's the most fun I've ever had in the snow.