After looking at this, here are some insights (1604 retail addresses):
At 0x1403D9F57 there is a some logic for recreating the radio emitter. In addition to some vehicle hardcodes 0x149BD32A (pbus2), 0xEDA4ED97 (blimp3), there is also a check for a specific flag: *(audEntity + 164) & 0x80) != 0 …
This value is set in: 0x1403D9C94 and 0x140F50284: which checks if the entity has a PLAYER_VEHICLE decor value (i.e., one that exists; value does not matter). There are likely some more features dependant on this decor that could probably be searched for.
Also, 0xC1805D05E6D4FE10, 0x2F7CEB6520288061, and 0xDA07819E452FFE8F are all natives related to radio emitters, its low-pass/distance threshold, etc.