On both my Mac and Linux setup (mpl 1.5.0) is appears that the bold version is selected over the regular one, as both are understood to have the same weight.

See this question on StackOverflow where I described the problem and the "solution".

http://stackoverflow.com/questions/33955900/matplotlib-times-new-roman-appears-bold/33962423#33962423

Please close this issue if this is an actual font problem unrelated to mpl.