Never experienced it myself, so I would guess no. Maybe there is a way to trick the editor into accepting it, but it seems to me it was never intended to do that. Importing a second .dae file wipes the previous one (as you've probably already noticed).
You can try editing the ent file through text, and duplicate this entry:
<Mesh Filename="model.dae">
<SubMesh Active="true" ID="0" Material="" Name="pPipe1" Rotation="0 0 0" Scale="1 1 1" SubMeshID="0" Tag="" WorldPos="0.0219399 0 -0.0853681" />
</Mesh>
I strongly suspect that this will render the file unparseable by the editor, but you might as well give it a go.