Has anyone ever tried useing epoxy to fix cracks in windows. Something along the lines of this https://youtu.be/ryN2U-yJAu4 (note I'm not endorsing any particular product or affiliated with the organization that makes or market this product) I am wondering if this would be a good way to fix cracks in the windows of railroad equipment.

This stuff does, indeed, work on automotive windshields, with results varying/depending upon the quality of equipment used to impose the vacuum upon the cracks.

FRA railroad glazing is not (necessarily) the same as automotive windshield glazing.

As an ad-hoc repair I've just painted West System epoxy on window cracks and they stopped leaking. Wasn't pretty though. Wouldn't expect it to hold up under car movement.

FRA glass is not glass and should not be repaired with products intended for glass. Your application may not require FRA glass. Check your regulation books, especially the Applicability section.

You have not said much about what kind of car this is with cracked windows and why they are cracked. I worked on wooden cars with double length upper sash glass that cracked. The cracking was caused by a very flexible wooden body. We used a special RTV that never gets really hard. Put tape on the outside and injected the RTV into the crack. When it had set up the tape was removed and a razor blade used to clean off any excess material. This worked fine until we replaced the glass with tempered glass, which is about ten times stronger than regular annealed glass. Also much safer. If this is laminated glass do not use RTV as it will fog the PVB layer. The annual safety inspection of the cars allowed operation with cracked, not broken, glass as long as it did not result in a sharp edge.

I have seen small bulls eye cracks in locomotives before and wondered if this Would work, however this is for a CV caboose window.