Based on the 900_900e comparision chart, the 4243908F2 can support 4 WAN T1 circuits or 4 TDM voice circuits for terminating T1/PRI to a PBX.
The maximum number of calls would be limited to 60 TDM to IP conversions on the model you are using. I have attached the sheet for reference.
4 PRIs yes. 92 concurrent calls, no. There are 60 DSP resources in hardware, each of which can handle one RTP-TDM call. We've never pushed 60 but I seem to recall a couple of DSPs reserved for internal use. T.38 fax is limited to 30 concurrent. It'll do two PRIs plus a handful of FXS ports at the same time just fine.
Also no NFAS. Each physical PRI needs a D-channel.