Yes, but I suppose even if you have 7 that line up, they may not fall in your band.
To remove that constraint, so it's just any band, I think it should be more like: given a cathedral is in a particular place, how likely is it that six other cathedrals fall in a 50km wide band aross Europe.
Okay, GPT4 said there a just 189 non-overlapping 50km bands (horizontal, vertical, and diagnoal) in Europe and then continued to calculate the chance to land those 7 points in any of the 189 bands and gave a result in the order of 10^-12.
I think if you set the probability of the first one at 1, then the rest works perfectly at any angle of band. I could be wrong, but intuitively that seems correct.
search box tells me 600 choose 7 is 5e15, which implies (if google and GPT4 were correct) that there ought to be on the order of thousands of fat lines containing 7 actual cathedrals
To remove that constraint, so it's just any band, I think it should be more like: given a cathedral is in a particular place, how likely is it that six other cathedrals fall in a 50km wide band aross Europe.