Yep, it's been there about a week now. It seems to be jumping back and forth from one side of the tunnel to the other -- it was on the other side just before the French border for about three weeks, now it's back on the other side just after the river crossing.
I was joking to my wife that the Basel border is becoming something of a revenue generator. The French police often install a speed trap just before the border (in the new 70km/h zone), then you've got the temporary speed camera in Horburg tunnel, then you have the permanent speed camera just after the Horburg tunnel exit.
And then, just for good measure, they'll stop you as you get off at the Badischer Bahnhof exit to make sure you've got your new vignette.