Of course, while you can't track a JumpShip's trail, you can detect one coming before it appears iirc. In an interesting, causality-breaking way - despite the jump being instantaneous, to the point that theoretically if you had a HPG on recharge stations at both origin and destination you would be able to have a real-time chat with someone at the other end and the instant the jumper flickers out of existence at your end it pops into existence at the other, the other end could detect the incoming jumpship for anything from seconds to hours, depending on the mass that's jumping - to the point they can detect the incomer not only before the jump, not only before the button is pressed to initiate jump, not only before the capacitors start dumping energy into the core to get ready for said jump - but before the decision is made to jump at all. The jumper might have been hanging out at the jump point for weeks waiting for a dropper to arrive, and then a warship or another jumper loaded with assault droppers and ASFs jumps in, and the captain of the civilian jumpship orders an emergency jump out - but because they've got two behemoths and a mammoth hanging off their collars when they press the button, the place they jump to has been detecting their arrival for the last day and a half.
Raises interesting questions about the nature of hyperspace and reality, as well as the existence of free will in the Battletech universe.
Of course my memory is horrible, so I might have remembered this as how it is in the Battletech universe when it actually belongs to an entirely different fictional universe, but considering I've seen it used in a fanfic recently and all the discussion around it was about the other things that happened in the chapter, not how this wasn't how jumpers worked at all and the author was pulling things out their butt, leads me to believe that I'm remembering correctly - or at least that if I'm not, I'm not the only one.