The following syntax will work for SPTS files (not sure about MPTS)
ffmpeg -probesize 50000000 -i source.ts -map 0:0 -map 0:1 -map 0:2 -c copy destination.mp4
The probesize bit tells ffmpeg to look over lots of file for the I picture, otherwise on long GOP it seems to give up sometimes. (like most decoders, ffmpeg can't start to decode until it finds an I frame)
Using -map 0:0 -map 0:1 -map 0:1 -map 0:2 tells ffmpeg to select/map specified input streams to output in that order.
Using -c copy mark all the streams to be just copied to the output