Basically, the decoder will try to find some error at bitstream, and also tries to substitute invalid area by copying from reference frame. But it does not have sophisticated error concealment algorithm on it.
We tracked this request on futureimprovement, but at this moment, still no schedule on when to add the feature.
Most of the recovery code are actually related to h.264 decoder. You can find the following function in H.264 decoder, and related function calls to this functions.
RestoreErrorRect(Ipp32s startMb, Ipp32s endMb, H264Slice * pSlice).
For MPEG2/1, no similar work. If you want to work on some improvement, I think you can start from the MPEG2VideoDecoderBase::DecodePicture() funciton, and if the decoder find some error, you can add some recovery code.