A lot has been written on this topic. Here are the citations for the most pertinent ones for you:
Warner JL. Recentralizing phlebotomy back into the laboratory. Clin Leadersh Manag Rev. 2005 Jul 26;19(4):E3.
Southwick K. Back to the drawing board: hospitals rethink their phlebotomy staffing practices. CAP
Today, February, 2001.
Other articles appear in the back issues of Phlebotomy Today, accessible at www.phlebotomy.com (fee applied). Good luck.