Hi Daniel,
You are welcome! Unfortunately the source is JR Hokkaido Kushiro Sub-headquarter's website and it's only in Japanese. However I would provide more information.
The SL train is named SL Fuyu no Shitsugen Go - SL Winter Wetlands. It still in operation every day but as I have said in the previous post, it ends on March 9 (Sunday next week).
To board on the SL Train, passengers are required to purchase reserved seat tickets with costs of 800 yen for adults and 400 yen for children (12 year-old or younger) as well as ordinary tickets. Reserved tickets are available at JR Stations' Ticket Offices (Green Counters) and JR Travel Agencies.
Enquiries can be made to:
JR Kushiro Station on 0154-24-3176 (5:30-22:30)
JR Shibecha Station on 015-485-2018 (6:50-17:00)
JR Twinkle Plaza (Travel Agency) Kushiro on 0154-25-4890 (10:00-18:00)
Please feel free to ask me more information.
Cheers :)
Yoshi