Reading Extension data from MXD

Is there a way to read extension data stored in the MXD in Python?

We have a third party extension to ArcGIS. This extension stores information in the MXD according to Esri guidelines using the stream.write/stream.read capabilities of the VariantStream object.

We are trying to make our extension's capabilities accessible through a python session. However, there doesn't seem to be a way to get to any third-party extension data persisted in the mxd, or at least it isn't obvious to me.

Is anybody aware of a way to do this?

Thanks