Being kept on the payroll is entirely due to WARN, not a way to avoid it. WARN requires a notice period but there's absolutely nothing in any state's WARN statute that says an employer has to let you continue to actually work - only that you remain an employee. Generally, you'll stay an employee on regular payroll, etc, for the 30 or whatever number of days required, then the package will trigger, PTO paid out, etc. You will also lose badge, email, and systems access and be asked not to come into work immediately just like everyone else WARN or not.
You'll get an extra month HI out of it, but the month payroll you get for WARN will be deducted from the severance calculation - remember, severance outside of WARN mandates is voluntary. So you don't get paid for WARN AND get full severance based on years of service. You do get COBRA for 30 days in addition to regular HI while you are still an "employee" so there's that.
This is exactly what happened when WARN was triggered in January, talk to some folks who were RIF'd then.