A flat we lived in for a couple of years until 1985 had 'quiet mains' until about 11:30 PM on weeknights (and on Sundays) at which time a large bakery down the road would start work for the night and we'd start getting occasional 'glitches' (short and quiet zzzp sounds* like you'd get from an old fridge wth no suppressor) and the amp would start humming quietly. This would persist until about 5 AM so it was never a real problem. During our time there the bakery closed down and it stopped.
The house we've been in since then has never had any mains issues. Even reputedly hum prone amps, like my old Rega Brio ('clamshell' version from 1996 - 2007) and my Nait 5i, never suffered at all. (Even when listening very closely with the volume turned right down.)
Whether you get a 'noisy' mains supply seems to be a bit of a lottery and whether your amplifier will cope with it is even more of a lottery.
*I remember buying an MK mains plug (fitted with a VDR) from my hi-fi dealer and fitted that to the 4-gang MK extension I used at the time for the system. It did reduce the volume and intensity of the 'zzzp' noises but the bakery closure had the greatest effect. (Sadly for the lost jobs that resulted.)