I doubt they'd be tolerated if they spoke out loud about being atheist, no. I used to live in an Islamic country, an Arab state where Islam touched every aspect of daily life. There was one 'religious complex' in the country and it catered to every religion that was not Islam. This was held up as some sort of huge act of tolerance and generosity on the part of the country and its government. It was stuck in the middle of nowhere so Muslims would not have to see it, or to accidentally have to hear any hymn singing or preaching. All non-Muslims had to share the space and take turns to host their group worship. This did not extend to Jews and anyone unlucky enough to be Jewish and living and working in that country would be best to never speak of it. The building was not permitted to display crucifixes or any other religious non-Islamic iconography.
In contrast, on Fridays, loud hailers would blast out Islamic preaching from the mosques for most of the day. Not just the call to prayer, but broadcasting the actual preaching, very loudly so wherever you lived you would hear it.
RE was not taught in any school as a general subject. Only the Quran and Arabic, which was obligatory for every pupil whether they were Arab or Muslim or not. It was literally illegal to mention the existence of other religions in schools. It was illegal to have any books in schools or public libraries that mentioned Christanity or any religion other than Islam. It was illegal to own more than one bible for your own use in case you were thought to be distributing it in an effort to convert Muslims. You could be (in theory at least) arrested for carrying your bible outside of your home, unless you could show that you were on your way to a private bible group or church service. Any sort of mention of Christianity or any other religion in public outside of a private prayer group was also illegal.
They loved the idea of 'the holidays' and the shops were full of Christmas Trees and decorations, but it was never spoken of as Christmas. Just 'the holidays' Even in the international schools you could not openly hold a carol service in case it caused offence to any Muslim pupils.
If we needed to enter any sort of government building for example to extend our visa, or whatever, we were expected to have our arms and legs covered to below the knee and the elbow. This was for men as well as women. It was often the same in shopping malls as well, although in latter years they became a bit more lax. You could have to police called on you for a peck on the lips on public, or for embracing someone of the opposite sex.
As you can imagine, I do roll my eyes and tut when Muslims in the UK complain about racism, Islamophia and a lack of tolerance in this country.