Holy shit, Threnody is an awesome song - I've always just loved how haunting the whole thing sounds. Do check out Penderecki's choral music, too, as it's just... chilling and amazing, especially how he uses microtonal choral techniques throughout. He's a great composer, and I highly recommend listening to more of his work.
That all being said, the technique that's being used at 1:58 is pretty tricky to emulate, because the string players are plucking above the "nut" (the part where the strings rest at the top of the neck... I had to look that name up). The strings don't have a controlled tone at that point, so it sounds relatively random and percussive. I haven't seen a sampler yet that deals with more modernist uses of instruments like that, though I certainly could be wrong (I don't use a large variety of samplers myself).
If I had to try to emulate it, I would try to get a very dry pizzicato sample, and play relatively high notes that are randomly detuned. Set four pizzicato notes up like that and play only those four notes; there are only four strings, and you CAN'T reasonably change the notes being played in real life (as you can't finger on the bridge to produce different notes past that point on the neck). Be sure the samples have a quick decay, as the notes are unable to reverberate due to their short length (physically).
If you're up to it, you can get similar sounds by plucking a tightly pulled rubber band. If you have a decent recording setup you could create a serviceable sample that way, too.
Hope that helps.