You can get the C++ code for computing LBP using OpenCV's Mat data structure here:
http://www.bytefish.de/blog/local_binary_patterns
You should be able to find the Python version as well on the same site.
The code is written by Philipp Wagner, who I believe contributed the face recognition code you mentioned to OpenCV, so it should be the same thing.
The LBP code is found in the file: OpenCV-2.4.2/modules/contrib/src/facerec.cpp as a static function. Unfortunately, it does not appear to be exposed for public use (at least for OpenCV 2.4.2).
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