To answer the question in the OP, I wouldn't be too concerned. The safety requirements are presumably just as stringent (relative to the threat) as any other utility. The contractor or whoever is involved in procurement will presumably have some experience. [..]
Yes you could potentially die in a battery explosion toxic gas cloud, but do you know the likelihood of that happening? Probably more likely to die in a freak gasoline fight accident.
1) You have no idea whether or not that's true.
2) Even it is (and there's no evidence that it is), the result would be wildly skewed by petroleum products being far more common and far more widespread than huge battery banks with a capacity of at least a few GWh. It would, therefore, be irrelevant to the likelihood of each close to such a battery bank.
3) The use of shipping containers doesn't inspire confidence that this is a well designed facility that takes potential risks into account. The idea that an extremely fashionable thing is subject to the same scrutiny as an extremely unfashionable one obviously isn't true, so it would be unrealistic to assume that it's subject to the same safety requirements applied equally stringently.