Indeed. With a transfer to Riehen on the tram and then the S-Bahn from the Bad Bahnhof. He asked me where I was going, in German, didn't really wait for the answer and switched to French. I replied: "Riehen". Then he asked me "Where". Then I said "I'm going to Riehen, it's next to Basel, you know?" (Ich fahre nach Riehen, neben Basel, weisch?) He already knew a was a Swiss citizen, as I had shown him my ID card. After he fled, I had a giggle to myself. :D But seriously, he should know where Riehen is, as there are only three incorporated communities in the Canton of Basel City (Basel, Riehen, and Bettingen).

I think these are more likely to be immigration types, who wander around checking the documentation of...people they feel they need to check the documentation of. I have seen them in action on that very route as well as on Basel-Bern, always routes heading away from Basel. They once hauled people off the train in Olten.

I've seen some customs people with an appalling manner on the Domodossola-Brig-Sion train. Usually I like Swiss people, even those in officialdom, but this was way out of line. They ignored me fortunately and hauled some other people off the train. Remember what I said about criminals in uniforms (this is probably more about people letting the power going to their heads).

The line through Domodossola to Brig has essentially two types of travelers: Locarno (via FART) and pax originating in Italy (south of Dom,). A customs crew boarded in Dom., there was a Chinese pax. in the coach I was in who had to show the money in his wallet.
They didn't bother me. A tourist originating in Locarno heading to Brig might not even be carrying his pp, could potentially be in "trouble".