I don't want to burst your bubble, but this is oftenly used technique in comics, where they take photos of places and put filters and additional outlines to it. To be honest i prefer it this way as it lessens the burden on the artist who has such thight deadline and lets her focus on character better. The efficiency is the key when the script and quality is this good as they only have about a week to complete the whole process.
Well I don't mind. I still love that they care about backgrounds enough to use real photos.
That is true but I believe I read somewhere (long time ago when the 1st couple story was ongoing) that the author went to Prague and also the way those scenes are done makes me believe it could be based on real pictures and experiences by author herself since there is for example a swan and ducks in the raws in one panel which otherwise would be completely random selection of animals but not for someone who visited Prague, also in ch. 46 there is basically an edited photo taken from a residential building with a view of Powder Tower and a picture with a Czech sign saying "pedestrial zone" haha.
It definitely seems like photographs which are then edited, it is most probably not drawn from scratch but I believe the author made the selection of the pictures and it is not some random picks of background by helpers (which also happens a lot) which makes it great and authentic
Oh god. I love the backgrounds. I'm local in that area, and I love recognizing my everyday sights. It's really nice that the author put this much into researching and drawing backgrounds so accurately.