Ive got nearly 20 years part time.Once a laid off 5 year seniority company time full timer tried displacing me on my job and the center manager told me he could.Well a call to my business agent and the next day I was back to work with a free day of pay.So no, lay offs go by company seniority. A full time with less company time can not displace a part timer with more company time.Been there done that!