People planning their summer travel have noticed that travel on certain routes (for example, Brig and Milano is not straightforward. This SBB webpage has information on routes in Germany, Austria, France, and Italy that will be affected by construction this summer:
https://www.sbb.ch/en/travel-information/rail-traffic-information/timetable-change/europe.html
More information, including other countries (UK, Norway and more), is on this page:
https://showmethejourney.com/travel-news/a-summary-of-major-construction-projects/
Specific information for Switzerland by date, including strikes in neighboring countries (like the strike in Italy today):
https://www.sbb.ch/en/travel-information/rail-traffic-information/operations-disruptions.html