They happen. During a period when USPS was paying over $120,000,000,000 too much to OPM for current and future retiree benefits, we had SEVERAL RIFS in the USPS and I saw hundreds of people lose their jobs and get tossed on the street.
They are a bit more common in DOD where missions may change and bases may close ~ overnight!
Yes, federal layoffs happen. Is the probability of the average federal employee being laid off this year, higher or lower than the probability of a private-sector employee being laid off?