I can’t confirm to 100% what you are saying but I’ve also never seen a ED_ERR_PHY_TIMEOUT when using GPRS.
I think the ED_ERR_PHY_TIMEOUT is only used in GSM mode when the modem negotiation takes too long time (or fails to negotiate at all).
Compare this timeout to S-register parameter S7 in a “normal” PSTN modem (wait time for carrier).
In a GPRS connection, I think you always have some kind of error code between the ME and the Nwk if something goes wrong. The similar response code if something goes wrong in GPRS are ED_ERR_GPRS_ABORTED or ED_ERR_WM_GPRS_OPEN…
But I think everything should be clearer if Wavecom included a note in the development documentation if the result codes are for GSM- or GPRS mode…
…not only for the ed_DialupConnectionStart() but also for other relavant functions.