You will have to recompress the video. The quality varies by encoder.
And Blu-Ray .m2ts files are MPEG-2 transport streams which may contain MPEG-2, VC-1 or AVC encoded video. You will have to determine the video type if you want to get the best downconverted quality.
Barring that, you might have to ask the others as to which encoder/transcoder they use for this purpose.