It is – at least on a Mac, tested it on several maps 🙂
When you load a save-game, the decimal representation of the seed used to create it is put in to stdout.txt.
Converting that to base 36 using link above gets you the alphanumeric version of the seed, and using that format you can start new games and get the same map.
I my case the seed in stdout.txt was 1446600056 which in base36 is nx9nqw – using that alphanumeric version of the seed gets me the exact same map, in many cases even with same city placement and even city names. I also tried medium and small sizes and it seems that they result in cropped versions of the large size (at least on a Mac, I appreciate it’s likely different depending on operating system).