I moved a database from MS Sql Server 2000 to Postgresql a few years ago via BCP files. I used a Python script to do some fixup on the BCP files to make them importable as CSV files into Postgresql. I don't know if quirks I ran into are still an issue with newer versions of Sql Server but for what it's worth, here are the comments from that script:
Do you rember what the encoding of the files was by any chance?