PHILIPPINE NATIONAL CONSTRUCTION CORPORATION AND ATTY. LUIS F. SISON, PETITIONERS, VS. NATIONAL LABOR RELATIONS COMMISSION, ELIZABETH N. LOPEZ-DE LEON, JANICE DAY E. ALEJANDRINO, SABINO B. BASSIG, CRISANTO D. CALIMAG, GEMMA C. CORDERO, JAIME C. DELA CRUZ, ROSALYN S. DELIVIOS, FELIX M. ERECE, JR., DEMOSTHENES F. FAMINIANO, LOIDA G. HERNANDEZ, ALMA S. HUGO, RONALD E. JAVIER, MARK D. LAGO, ALVIN NICOL D. LIBONGCO, FREDERICK CHARLES Y. LIM, VIRGINIA G. MADRONA, ANTONIO C. MANLAWE, FLERIDA A. MEJORADA, RENATO M. MONSATO, YOLANDA C. MORTEL, VENJIE E. NAMOCATCAT, DOLLY C. NEPOMUCENO, AMANDO M. ORALLO, VEGNETTE U. PACO, MOSES M. PANGILINAN, MIRIAM M. PASETES, HENRY B. SALAZAR, ARNNE NOBERT C. SILVESTRE, ELMER M. SIMBULAN, JEAN P. TALUSAN, SUSAN R. VALES, AND PAUL C. VICENTE, RESPONDENTS