To compute the channel capacity, you need to know the channel's signal-to-noise ratio as well as its bandwidth.
The Shannon channel capacity formula is: C = B * log_2(1 + SNR) where C is the channel's capacity in bits/second, B is its bandwidth in hertz, log_2 is the base-2 logarithm and SNR is the channel's signal-to-noise ratio.
If we assume an SNR of 48 dB for a reasonable POTS line, its capacity would be C = 3 kHz * log_2(1 + 48 dB) ~= 3000 * log_2(63097) which is almost 48,000 bits per second.
This is a theoretical limit that realizable systems can only approach, but never equal or exceed. A practical system would also use extra bits for forward error correction purposes; I doubt that this codec deals gracefully with bit errors.
For back-of-the-envelope purposes, assume you could use this codec to send a single voice signal in 700 Hz of bandwidth on a channel with low SNR, or you could send 60 voice signals over a regular POTS line.