What are the border definitions in the Ramachandran plot? I've heard some people mention that this or that program isn't "up to date" with respect to the borders used in the Ramachandran plots to classify &phi;/&psi; as being in the most favorable/acceptable/disallowed regions.

How are the accepted regions defined?  What is the current accepted paper that covers this?
I wish I could answer your question outright, but this is outside my area of expertise. The best I can give you is a place to start. I expect any recent book on proteomics would cover this topic. For example Introduction to Proteomics: Principles and Applications (Methods of Biochemical Analysis) by Mishra and Blobel, Wiley 2010.

I found some promising papers with a little searching with SciFinder. Neither I nor my institution subscribe to Protein Science, but the abstract looks promising. I have skimmed the article in PNAS. Hopefully one of these articles has your answer. 

Zhou, et al, "Revisiting the Ramachandran plot from a new angle", Protein Science 2011 1166-1171.  

Porter and Rose, "Redrawing the Ramachandran plot after inclusion of hydrogen-bonding constraints", PNAS, *2011, 108, 1, 109-112