I have a slightly different view. The grammar that you describe does not seem to be a bad journey, given that presumably many of them will be doing the 20 minute walk at the end together. A 15 minute walk to the station, then a 20 minute train journey seems ok to me (coming from London where many of my friends' children at local comprehensives have a similar journey, simply because of the traffic). But I can't imagine being in a position where the cost of the indie wouldn't have a very negative effect on my family and lifestyle - if it wouldn't impact much then I can see that the slightly shorter journey time (1/2 hour compared to 1 hour) could be beneficial.
In terms of local friends, I agree that it's handy to have local friends but beware of local friends with poor public transport. Of my dd's friends, one is 6 miles away and a very simple bus journey. One is 7 miles away, 22 minutes in the car, but 1 hr 20 minutes by public transport. Another is less than 3 miles away, 7 minutes in the car or 1 hour walk (on roads with no street lighting or pavements!

) - but almost 2 hours by public transport! My dd is very independent and mostly travels alone to see her friends but I'd rather she was visiting the ones further away!