No, they are definitely not upscales - the BDs come from the same master as the 2004 DVDs - the 2004 DVD master was done in 1080p and some HDTV stations did broadcast it in 1080i, so those are native HD (high quality HDTV captures are now available on myspleen).
And there were native HD broadcasts of LOTR as well but only TTT was shown in the EE version - so the EEs found online were usually 1080p for the theatrical scenes and DVD upscales for the extended scenes.