Looks like the exact opposite has been shown to be true - I wonder why?
I've got quite a few Midlothian-based colleagues who are close to the railway (Bonnyrigg, Newtongrange etc.) and none of them seem to use the train to commute, for them an early start to "beat the traffic", hop in the car at their front door and get out at the front door to the office in 25-odd minutes is much more efficient and reliable than walking or driving to a station to get on a quite possibly late or cramped commuter service then walking the 15 minutes to the office (potentially in the rain) at the other end, only to repeat at the end of the day. Unless you were working in central Edinburgh, where it's harder to park and you have a long, slow drive in down the "arterial routes" like the Dalkeith or Liberton Roads, I can't see the attraction for those working on the periphery of the city with good, direct access to the bypass at either end and big main roads around Bonnyrigg. A train commute would be slower, less reliable and more expensive for them.
It does seem to be popular with them for day trips / nights out to Edinburgh though - I'm not sure if they ever head south on it though, for some that part of the map is still blank with "HERE BE DRAGONS" written on it.