But that would be baloney, wouldn't it?
Looking at a warp chart of the warp charts for TOS and TNG, in TNG time (still so in Voyager), warp ten is infinite, you'd be occupying every space in the universe at once.
Warp 9.99 in TNG is 7,912 "Cochrane units".
Warp fifteen in the TOS chart is 3,375 "Cochrane units".
Warp thirty would put it well beyond infinity. There would be no delay across the entire universe.
Warp 9.9 = 4 billion miles per second which equates to about 21,473x c (from VOY, the 37's).
Warp 9 = 1,500 c.
Warp 8 = 1,000 c.
Incidentally, VOY displayed (on-screen) that it can only sustain 9.75 for 12 hrs (in episode 'The Swarm').
And since ENT-D was rated at about 9.6 being its 12hr sustainable speed... its a lot more reasonable to think VOY (a newer design) was never capable of 9.975 (which was in practicality never actually seen - only mentioned a handful of times and was likely a mistake).
Even in Threshold episode, VOY's maximum limit was 9.9 for about 45 seconds (and the computer warned that structural collapse would ensue in 45 seconds which forced Chakotay to reduce speed to 9.5).
It makes a lot more sense that speeds begin increasing a lot more the closer you get to 9.9 and then PAST Warp 9, each increment (aka, 0.01 increase) results in doubling of speed and power requirements.
So, Warp 9.91 = twice the speed and power consumption of Warp 9.9...
9.92 = double the speed and power consumption of Warp 9.9.
Anyway, for subspace comms or sensors, I think its somewhat different approach on how they USE subspace to attaint real-time bandwidth across numerous LY's - so actual bending of spacetime is likely just 1 method of a physical object achieving FTL speeds - but sending out comms or sensors doesn't need the same approach - also, usually comms and sensors have different mass properties than physical objects - starships need to reduce their inertial mass using sublight to achieve 75,000 km/s speeds, and also to use Warp.
I suspect you don't need to do the same method even if your sensors or comms use particles (because you have massless particles like photons) and their mass is proverbially negligible by default - so its probably a lot easier to have transmissions or sensor beams use subspace than it is to make a physical object like a ship to use it for FTL.
VOY was able to scan in a radius of 40 LY's (the ENT-D had about 25 LY range)... but its possible this wasn't real time - or at least, not exactly, and subspace comms move at very high speeds on the Warp scale - but the speed varies across centuries and is tech dependent (aka, base emitter which sends out the sensors and comms).
So the NX-01 was severely limited in subspace comms without amplifiers - but we do know from episode Regeneration that a subspace message would take 200 years to reach the DQ... but in the 24th century, VOY was said that their message to Earth would have taken YEARS (not decades) with standard subspace comms (this is likely because the ship's comms/sensor array was far more powerful vs what was used in the 22nd century) - but for VOY there were other practical limitations on sending a message like that across the galaxy - a single ship, cut off from support would be a prime target for opportunistic species, and the Kazon were on the ship's back spreading rumours - so for them it wasn't entirely practical - and subspace comms can also be deflected or degrade by a lot.
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