I'm not saying it can't be done, clearly it can be done otherwise this article wouldn't exist. But it is not quite as easy as pointing a magic wand (aka an antenna) at a highrise and saying '14th floor, apartment on the North-West corner', though that would obviously make for good cinema.
Subpoena the power, water & gas company, and look at apartments that have unusual power usage, coupled with almost zero water & gas usage. Especially look at apartments that don't have a spike in power usage in the morning & evening that corresponds to people having a regular commute.
I'm not sure how much power this equipment draws at idle - I'm assuming it's more idle at night, no need to send scammy SMS messages at 3am Eastern - but I'd wager you could track that.
Granted, it's not fast, but depending on how quickly the companies bend over backward for such a request & how good your interns are at using Excel, you might be able to get this done before sundown.
For those who have not seen it before, Waterwitch is on page 43 of the 2013 catalog here [1], and is described as "Hand held finishing tool used for geolocating targeted handsets in the field". It did seem to require, if I'm reading right, that the target be connected to a malicious GSM router called "Typhon" (page 42).
[1] https://www.cryptomuseum.com/covert/bugs/nsaant/files/NSA_AN...