Use the search function in Windows Explorer and filter by files changed on the date of the update, and you'll see what files have been changed
Yes, about 700MB were patched from a small download size. With the recent Steam updating process which is patching instead of replacing files and thus saving bandwidth, sometimes the datestamps are not being updated. So I have no clue what was changed.
Must be a route as mine updated on Nov 25th and nothing scheduled either. No change in my installation during the past week except for a QD scenario, cache files and a tile extracted by said QD scenario.
Yes a small download just over 200 MB but uncompressed about 1 GB. Yes, I have both the route and the loco.