Traveling between worlds in the system takes 1d6+2 Days (Core pg 291) while system wide communication takes 1d6-1 Hours (Core pg. 430).
Is there any reason a ship travelling in the Drift for 3-8 days can't communicate with someone on a planet in that system, on a non-drifting ship, or even with a ship that is also drifting with messages taking 0-5 hours to travel between communication arrays?
By RAW, I can't find anything limiting it, but I'm wondering if I've missed some rule that communications don't function while in the Drift.