Now you can't pass parameter to matrix using Parametrized Remote Trigger Plugin (https://wiki.jenkins-ci.org/display/JENKINS/Parameterized+Remote+Trigger+Plugin), even in case you will pass parameter with name that the same as you specify in Matrix Combinations Parameter, matrix will be totally deselected and no builds will be launched.

E.g. if you specify MY_MATRIX_PARAMETER as name for Matrix Combinations Parameter and then try to reach remote url http://jenkins.yourdomain.com/buildByToken/buildWithParameters?job=your_jon&token=your_token&MY_MATRIX_PARAMETER=OS=="win7" your Matrix Combinations Parameter will not be set (all others parameters can be set as usually).