Most satellite/cable services use AC3 or MP2. MP2 can't be bitstreamed to receivers so it's always decoded to PCM.
No broadcaster would use PCM, as most SD channels are only 1-3Mbps to begin with.
Indeed, it has to be a compressed format.
To determine the bitrate of a PCM stream you just take the sample rate * the bit depth * the number of channels.
48000 Hz * 16-bit * 2 = 1,536,000 bps = 1.5Mbps
44100 Hz * 16-bit * 2 = 1,411,200 bps = 1.4Mbps
Knowing the bitrate and the number of channels, there are two unknown variables. We do know that with no compression, you're essentially looking at two mono channels. Meaning each channel would be 32kbps. Yeah right!
Even unlistenable-quality mono PCM audio is greater than 32kbps.
8820 Hz * 4-bit = 35,280 bps = 35kbps