According to a report on RTS radio on 1 February 2021, French border staff are not systematically checking people entering France by road or rail from Switzerland.
On Friday, 29 January 2021, the French government announced it was closing its borders from Sunday to all those outside the EU or Switzerland. In addition, except for cross-border workers, all those entering France from within the EU (or Switzerland), would need to show proof of a negative SARS-CoV-2 PCR test done in the last 72 hours. A week before, France announced the same measures for people arriving by air and sea but not by land. The recent measure covers all forms of entry into France.
However, according to a report today by RTS, there seems to be little in the way of checks. A number of people who have crossed the border report not being asked for either proof they are cross-border workers or proof of a negative SARS-CoV-2 PCR test result.
Systematic checks would slow cross-border traffic. However, RTS reported no slow down in cross-border road traffic at Perly, one of the border points near Geneva.
On certain trains it seems there were no systematic checks either. Announcements were being made on trains regarding the requirement to carry a proof of a negative test or proof of cross-border work, but there was no evidence of systematic checks.