I don't think it depends on the plan. Looking at the U.S. Code §72(t)(2)(A)This may be true... or may not be true. It's up to the plan. Please verify with your 401k plan documents whether you can withdraw between the age of 55 and 59.5 penalty free. The law states that plans CAN offer this provision to allow non-penalty withdrawals if you separate after age 55... but it is not required. So check your plan.
I would take the deal in a heartbeat.
(v) "made to an employee after separation from service after attainment of age 55," is exempt from early distribution penalty.
But I am not a tax guy, so who knows?