I know that it’s not carved in stone but using street imagery to update the map is not necessarily derived work, and license clash does not apply.
As in areas of life elsewhere: when you look at something, you learn something, and you are using this learned information to create any work then it is not derivative work but part of the normal way of human learning and working.
On the other hand if you take the image and trace it using software, and store the result in the database then it would be derived work. Similarly if you take the image, put it into the background of JOSM and draw its features over then it would be derived work.
It is even up to dispute whether recognising signs count as derivative work (I’d lean towards the “yes” interprertation) since it is not technically taking bits of the original and putting them into the new.
I do not think the CC-BY-SA imagery license would make it illegal to work with it, as it didn’t when OSM tiles were CC-BY-SA published (not so long ago), as well as Mapillary or OpenStreetCam. (Not to mention Yahoo!, Bing and similar commercial imagery, where the commercial license did not matter as long as it has been permitted to be used in OSM.)