hello @Synthesis,
It might have turned out that the miniDP to DP cable I bought (pretty sure it was generic cable with no brand) is unidirectional. No note on it on package itself, but noticed the note on the page where I bought it.
I had (and still have) no clue that digital cables like this could work in only one direction. Still, I have no means to test it whether its true or not, since I do not have any device with miniDP output nor screen with DP input.
Next cable I'm about to buy and test in few days is Delock brand, but just to be sure I've asked the store if it'll work with linkbox or not before making the purchase.