A very recent unionization fight in Providence may provide for some interesting material, considering it got national attention within the library world, and throughout the country.
-- "E.G. Providence PL Votes To Unionize." By: Rogers, Michael. Library Journal, 1 October 2005, Vol. 130 Issue 16, p24-24, 1/4p.
-- "Providence Public Library Staff Votes to Unionize." American Libraries, October 2005, Vol. 36 Issue 9, p26-26, 1/3p
Other articles include:
-- "Clerical workers strike at Brown University libraries." American Libraries, January 1991, Vol. 22 Issue 1, p13-13, 1/3p
-- "King County Staff Vote to Unionize." American Libraries, February 2003, Vol. 34 Issue 2, p23, 1/5p
-- "Ann Arbor Approves Contract." American Libraries, December 2002, Vol. 33 Issue 11, p26, 1/4p.
Depending on how much information you want about the unionization process, you may want to contact the local unions involved in each one of the above mentioned struggles.
I would also suggest getting in contact with labor libraries for more information about libraries and labor unions throughout the last century (examples: Holt Labor Library, the Walter P. Reuther Library, the Institute of Labor and Industrial Relations Library, and the Southern Labor Archives).
Check out: "United We Stand: Preserving the History of U.S. Labor." Chepesiuk, Ron., American Libraries, January 2002, Vol. 33 Issue 1, p60, 4p.
The only other contact I can think of to get some great information on the history of unions in libraries is the AFL-CIO (American Federation of Labor/Congress of Industrial Organizations)–ALA Library Service to Labor Groups Committee. To get specific contact information, contact: rusa (at) ala (dot) org.
If you need help retreiving specific full-text articles, let me know. Hope this helps