According to the IBEW, Biden's involvement was significant.

http://www.ibew.org/media-center/Articles/23Daily/2306/230620_IBEWandPaid

“We’re thankful that the Biden administration played the long game on sick days and stuck with us for months after Congress imposed our updated national agreement,” [IBEW Railroad Department Director] Russo said. “Without making a big show of it, Joe Biden and members of his administration in the Transportation and Labor departments have been working continuously to get guaranteed paid sick days for all railroad workers.

“We know that many of our members weren’t happy with our original agreement,” Russo said, “but through it all, we had faith that our friends in the White House and Congress would keep up the pressure on our railroad employers to get us the sick day benefits we deserve. Until we negotiated these new individual agreements with these carriers, an IBEW member who called out sick was not compensated.”