Federal Officials Probe Stock Offer To Union Chiefs by Global CrossingBy TOM HAMBURGER and JOHN HARWOODStaff Reporters of THE WALL STREET JOURNALWASHINGTON -- More than two dozen union presidents were personally invited to buy shares in Global Crossing Ltd. as the international telecommunications firm was first offering its stock to the general public.It isn't clear how many of the officials took advantage of the 1998 offer, but it nonetheless marks an unusual collaboration between organized labor and one of the nation's most-highflying companies.Federal lawmakers are already looking into accounting methods at Global Crossing, which is in bankruptcy protection. Now, a...