Caltrans has to keep records of when steel structures are painted, and with what. If one is old enough to have (or be suspected of having) lead paint, the project becomes a significant one especially if it's over open water. Was a much bigger problem in the 1980s-90s; most steel structures Caltrans has were repainted (with lead paint removal) since then, at least once.4

As for upkeep, homeless encampments are becoming a big problem. Not only on railroads, but also on freeways. Fires start in them frequently that damage more than just the freeway property. Some nearly block on/offramps. There was a story recently in Sacramento where UP trains have to stop and proceed at minimum speed though the southern part of town due to extensive encampments crowding the tracks; the adjacent light rail line is better fenced, runs more often, and has actual occasional police presence which keeps the encampments a little more under control there. What ever happened to the UP Police Dept? The story has me thinking about that YT about a market in SE Asia that pulls back the stalls and awnings to let the train through then immediately puts it all back after it passes. And the blocked line is where Valley Link aka ACE would someday run in Sacramento. Oh well...