Does the WARN Act apply in the case of a government contract loss.

If the current vendor did not win the follow on contract but most of that workforce may be picked up by the winning vendor, is the losing company obligated to provide notice that they no longer have work for thier employees. If the losing company requires departing employees, that they can no longer support, to submit letters of resignation yet the emploees themselves have received no formal notice that they have no jobs with that company after a set date, will that negate the ability to draw unemployment since one effectively quit their job?