The m2t files are a mpeg stream which has been recorded directly from tape, so in this step there was no quality loss. I know that Avid and Adobe Premiere can import this format. Avid also exports it. Not sure whether Premiere does and about Final Cut I have no idea.
As for the import, try to rename the file to .mpg / .mpeg etc. This might work since it is a MPEG-2 video which every program should be able to read without special codecs needed. See here: [en.wikipedia.org
When it comes to exporting. I don't really know. If you want to export with the same quality, then you could try to export a mpeg video with the respective video resolution. If that doesn't work, you have to try and use other codecs and make sure that the quality loss is minimized.