If you can get a PDF version of the diagram, you should be able to redefine the target print size with better success. Just remember that any embedded non-vector graphics do not scale up. I've printed to that size with no problem on an Océ b/w large format laser as well as banners. I'm a Mac guy by definition so printing is second nature.
_E
You can get a PDF from www.lhotka.net/cslanet/download.aspx
However, that PDF was created by printing to Acrobat Distiller from within VS 2005. I don't know if the resulting graphics are vector or non-vector, as that probably depends on how VS 2005 printed them and how Distilller interpreted the printing...
Copyright (c) Marimer LLC