Here’s a variation of the Yeti module file that adds the bin folder to the PATH, and plug-ins to MTOA_EXTENSIONS_PATH:

+ pgYetiMaya any C:\solidangle\yeti\Yeti-v1.3.14_Maya2014-windows64
PATH +:= bin
MTOA_EXTENSIONS_PATH +:= plug-ins

MtoA uses MTOA_EXTENSIONS_PATH to find the Yeti extension for MtoA, and Arnold uses PATH to find the Yeti procedural.