There is one train type of all long distance trains that is not equipped with cameras yet.
And even if it would be, the police would not start an investigation just because of a simple theft, unless people were in danger.
The official procedure is to report the loss to the police, and then to contact one’s insurance.
If thefts happen, then in stations were the train stops for a few minutes and with great passenger exchange and passenger flux, while the bad guys enter the train, take the bags, and leave it again before the train continues.
https://company.sbb.ch/en/the-company/responsibility-society-environment/safety/basic-rules-when-travelling/pickpockets.html
Kind regards,
Roland