BS3 is only (CIR) committed bandwidth with a pretty strict SLA
BS3a and 3b (UFF) are (CIR) committed + best effort (EIR - Excess information rate)
BS2/2a generally has a CIR of 2.5Mb up and down. There are a few plans that have 5Mb and 10Mb CIR.
The EIR is the same for BS2 as BS3a/b. All best effort but there is very very little congestion on the UFB network. Likewise with ADSL2+ and VDSL, in the case of ADSL2+ and VDSL if they hit 95% usage for 5 mins on the backhaul they need to upgrade the capacity. Does not apply to legacy ADSL network with people stuck on BUBA /conklins (that number is decreasing slowly as they upgrade the last 400 cabinets of these)
There is 2.4Gb download and 1.2Gb up shared between all the users. Chorus are not putting more than 16 customers per PON for any new builds. UFF and Enable and some of the older Chorus stuff could be 16, 24 or 32.
BS3/a/b has a range of CIR from 2.5Mb up to 100Mb. Depending on the plan the EIR can be the remaining part up to 1Gb.
LFC won't deliver the BS2 and BS3 on the same ONT.