PowerVR SGX backward-compatibility with MBX

I just came across the presentation by Jay Lee (Director of Sales, ImgTec) from TI Tech Days 2009. There was a mention there that PowerVR SGX core is backward compatible with PowerVR MBX core for content. What does that mean? Does it imply that newer hardware (with SGX) will be able to run the code that was written to run on MBX. This question comes to mind keeping in view that OpenGL ES 2.0 is not backward compatible with 1.1.

SGX also supports OpenGL ES 1.1, including extensions which may be available on MBX platforms, such as IMG_texture_compression_pvrtc and IMG_vertex_program. However, extension support may vary between platforms.