If you select let's say electric rail type save the game, and load it on another day it will not be set to the same rail type so you likely place some normal rails before you notice that they are not the current technology you are using on your lines.
So it would be clever to include that in the save.
The new player's default railtype would default depending on his/her value for the "Default rail type" setting. The setting values "First available", "Last available", and "Most used" would query the server for the available railtypes and the company's usage amounts, while Last selected would default to "First available".
Although this would be nice to have, it isn't something we expect to fulfill in the next year, and on that basis I'm closing it. We do this to keep the project manageable, productive and fun. We hope you do understand. Thanks for contributing though! Here you can find more about how we handle feature requests.