Minimizing capacitive crosstalk in open collector quadrature speed sensor
Your main problem is that the relatively sharp high-to-low transition on an open-collector output could cause a false high-to-low transition on the other channel (when in the high state), by capacitive coupling between those two wires. Transition in the other direction is much less sharp and thus less likely to cause issue, as noted in that other answer.

Shielding each channel independently would greatly improve the problem. With two pairs, it is better from that standpoint to have a pair for Gnd and A, and another for Vcc and B (than it is to have a power pair and a signal pair). Individually shielded pairs will help, especially if the shielding is grounded.

There are options to be less dependent on cabling


Add capacitors to GND on receiver inputs; they'll act as a capacitive voltage divider for the cross-channel capacitance. However that can worsens radiated EMI and magnetic coupling.
Reduce the value of pullup resistors (also needed to compensate for the rise time increase caused by above capacitors). However that can worsens radiated EMI and magnetic coupling.
Add series resistors on inputs, before the above capacitors; these will damp the parasitic negative-going spike; value needs to be a small fraction of the pullup resistors. These also shift the input threshold down, wich is good (see below).
Choose receivers input threshold (measured at oard input) significantly below half the pull-up voltage, like 1/4 (or equivalently increase the pull-up voltage if the receivers can accept that), so that you have voltage margin where it matters.
Use receivers with hysteresis (which is a way to lower the negative-going input thresold, which is the one that matters in the above).
Use slow receivers, or software filtering of fast receivers; to some degree, this is a free substitute for capacitors or/and hysteresis.