[vidarh]

The train has been there since 1854 - it's along the oldest rail line on Norway.

It'd certainly have been a long trek before then (a day maybe?), but I think a lot of the distinction there is also socioeconomic - the West Oslo dialect is very much associated with the wealthiest part of town and the wealthy suburbs, and where there certainly were expectations around what was long seen as more cultured and educated language.

The line is actually very sharp in Oslo between the Eastern and Western parts of the city, and that initial gap is at least usually seen as socioeconomic , but the gap then gets even larger once you get further East and North.