My understanding is that even it is galvanic isolated noise can still coupled through the isolation transformers. The CMRR of twisted pair LAN is around 40 to 50dB per channel so some noise can still pass through.
At the streamer side, depending how well the LAN receiver is designed to reject those noise. If the streamer has built-in DAC, then additional isolation is needed to prevent noise coupled to the DAC section. There are optical LAN coupler which can completely isolate noisy sources but they are expensive.
Likewise for WIFI streaming, the WIFI receiver at the streamer side must be well shielded to prevent EMI interferences to the nearby circuitry, especially if the DAC is built-in to the streamer.