I’m planing a trip to France the n mid September My travel companion lived in France and said train travel in the Pyrenees is definitely worth trying
In which part of Pyrénées is-it easy, according to your companion ? Trains run at the foot of Pyrénées, not in the mountain, and so it's not easy at all to travel from west to east by train. What is possible is to go to a train terminus (Lourdes, Tarbes, Lannemezan) and there take a bus to reach the mountains.
There is 0 question in your post...
Perhaps the question is about the reliability of the "travel companion" ?