From a cultural resource/heritage management former student I find this topic really interesting. The A line is quite special but also come with a lot of problems and possible dangers.
The general idea(at least where I come from) to manage old constructions that can be considered of special interest/heritage is, if possible, to continue to use them but with an adaptation to current circumstances.
In this case, the cars could be fixed to better meet modern security standards, maybe run only on sundays and/or days when there is not a lot of people going from/to work. As far as I know these wagons are also made to be able to run as tramways, which is another option.
I used to live in Gothenburg, Sweden, where tramways have been around since 1879(by horse) and electric since 1902. The electric wagons from then and forward are still in use summertime for tourists and can also be rented. Tricky thing horse preservation.
Anyway, I think the A line trains could continue run, just not as today. Dont know if it is possible based on logistics, economy, saftey etc. These parameters doesnt always seem compatible with Argentina.