On the train I get, there are six coaches and there's a toilet in the first and last coach (or if it's peak time, they combine two of these six-coach units). The conductor says this:
There are two working toilets on this train.This is an existential sentence, asserting the existence of something (the toilets). This is what we need to know, along with the information that they're in coaches A and F. The extra fact that the toilets are working is also provided, and while it's arguably essential information, it introduces some other implicatures.
Take this alternative wording:
There are two toilets on this train.Wouldn't you assume that they're both working? OK, previous experience of British railways might make you wary of such an assumption, but the lack of an apology for an out-of-service lav would leave me reasonably confident that the toilets are at least working when we set off, whatever may happen to them later on.
This means that the extra information 'working' is not required: it can be inferred without needing to be explicitly spelt out, along with everything else in the world that is either not relevant or assumed to be true unless otherwise indicated (so, for instance, you don't preface everything you say with the assertion that you are of sound mind, telling the truth, in possession of the relevant facts, and that grass is green and so on). The fact that it's there means that we assume it's relevant in some way. What could it relevantly mean? Well, that there are some other toilets that don't work, perhaps. Perhaps there's a toilet in every coach but only the two at either end are in working order. Or perhaps - and this is more likely - the toilets are often not working, leading to a long walk along the length of the train, so the fact that both are working today is worth knowing.
Either way, it's not giving the right impression of the train's toilets (which are actually clean and in working order most of the time).