My read on Trid Phantasm is this:
You create an illusion of something in the space, complete with sight and sound, but you don't remove anything from the space. It is also a static AoE, unless you move it. That doesn't slide, or move with you, which will cause problems if you're being viewed at the time.
Now, what does this mean for people trying to use it to hide?
Creating a camouflage type deal, where as long as they aren't moving, they have a good chance of not being spotted by the corpsec that just walked into the hallway? That's cool, I'll allow it.
Actual invisibility, allowing them to move without being seen? No.
Creating an illusion in front of a camera to make it look like all is clear while the group slips past? Sure, I'm game, especially if the hacker isn't online for some reason.
Creating an illusion that the group is corpsec, and having it move with them? No.
Making your poor man's APC van look like a delivery vehicle while it is parked? Sure, that's fine.
Making the van look like a delivery vehicle while in motion? No.