Multiple cameras and RT

When i have multiple cameras and i set their order, everything works correct. Second camera clears the depth buffer and uses the first camera’s render as background. When both cameras have the same render texture as target, i expected to see the same result, but unfortunately, in this case the second camera seems to always clear the previous render. Is this not supported? Is it possible to do this efficiently in script?

Unity3D ver. 4.1.2

Seems to be fixed in Unity 4.2.0f4