T48 S/G SfB Questions

[jolouis]

1) T48S and T48S SfB are the same phones with different firmwares on them. The normal T48S is what you want for SIP, and when the time comes to go SfB then you can just get the licenses and do the firmware updates. T4xG series are discontinued, replaced by S series.
2) Not at the same time as different firmware is required. However, you can run SIP firmware for FreePBX now, and upgrade to SfB firmware for SfB later.
3) SfB is a completely different beast than FreePBX. You need to look into SfB and how it manages devices/configurations/etc. You might be able to use YDMP (or whatever they are gradually trying to turn it into) but personally I've never done that so no definitive answer.