Did you find any solution. I am also looking for this. I have posted similar kind of question here...and unfortunately no replies from ESRI.
here is my question..
Sorry for the delay on this.
The point collection of the multipatch can be found by creating a new IPointCollection4 and then looping through the geometries and typing each geometry to the pointcollection.
for (int i = 0; i < multiPatchGeometryCollection.GeometryCount; i++)
//here i want to know each geomteries Triangles count and it vertices
pPtColl = new Ring;
pGeom = multiPatchGeometryCollection.Geometry(i);
pPtColl = (IPointCollection4)pGeom;
// Cycle through the points pPtColl