You'll find lines or musical phrases which have been accidently or deliberately lifted from other compositions all through music, poetry, and prose. There is another current thread about a line in McCartney's "Yesterday" which is similiar to one in "Answer Me". Just think how many lines (and melodies) in folk music have been re-used.
Imagine the court proceedings which could be brought - although Anon v Anon would be rather silly.

There are lots of pieces which Dylan has lifted from elsewhere - but he was probably quite deliberately doing what folk singers have always done - probably to establish that in spite of having a different style of singing, he was still part of the folk movement.

BTW no-one seems to have mentioned:

If you're travelin' in the north country fair,
Where the winds hit heavy on the borderline,
Remember me to one who lives there,
For she once was a true love of mine.

Perhaps it just could have been lifted from "Scarborough Fair" - I know that he heard Martin Carthy singing it (as did Paul Simon) on one of his trips over to to the UK.