Hello Mau95
Firstly, welcome to the SBB Community.
The tickets you purchase are for a route; it is therefore irrelevant by which means of transport you will be transported.
When purchasing a ticket, you sign a transportation contract with the public transport company. With tjis contract the public transit company is obliged to get you from departure station to your destination, according to the itinerary as per schedule.
Consequently, tickets remain valid for the train replacement buses as well.
Simply follow the instructions on-site and plan more travel time to arrive at your destination. Check timetables again one day before travel.
https://sbb-tickets.cc/en/travel-information/rail-traffic-information/notes/additional-information-construction-work.html
By the way, you are travellinfg to Switzerland.
Kind regards,
Roland