There are two separate issues here:
1) mutual interference that might be filtered
2) unacceptable high saturation of the non-linear
Regarding (1) I am not familiar with
the relative relationship between mutual interferers
in these particular systems, but in general with
digital modulation, it is possible to operate even
co-channel with interferers that are only -10dBc.
Thus typically one obtains a Bit Error rate of say
1 in 10^-8 for a carrier to noise ratio of 10dB.
This arises mainly because the modulation is quasi-synchronous,
and the interferer signal clock will be out of phase
coherence and thus appear as just noise.
(2) the resulting non-linearity products might be
capable of being out-filtered using an elliptic
function filter with the rapid roll-off side of
the BPF placed between the two carriers.
At bottom, life is all
Sucking in and blowing out.