What strikes me (especially after your questin about "klimatkalkyls...", and which I would think is the most likely if it is the same document or project, is that it is some type of corruption of the source and that it should really be "3 mån", i.e. 3 months. That would at least be feasible in the first line with costs and schedule, and nothing would directly contradict it in the others.
But it's guesswork.

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Note added at 25 mins (2018-02-08 15:02:42 GMT)
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See my disciussion entry. I do not know how to edit this suggestion (or if it is possible), but in light of further data given later, 3:Man here refers to 3 rails on the train track where the middle rail is used for power transmission. (I.e. instead of the engine getting its power from overhead power-lines, it is getting it from the third middle rail)

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Note added at 26 mins (2018-02-08 15:04:02 GMT)
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... and this also means that my confidence level increases from the lowest of guessing to next highest of fairly certain.

I, unfortunately, can't verify this, but I have run across it many years ago. This is a method used for the power transmission to the engine. You can have either overhead air lines or you can have a third middle rail. I think the third rail system is most commonly used in subways. In Sweden it occurs in Stockholm subway.
I have a notion of having seen the explanation of why it is "3:man" also, but I can't for my life remember what it is.