If my neighbour accepts a quote for an Individual Premises Switch at the same time as I do, does this reduce my Individual Premises Switch cost?

Yes, subject to several conditions.  nbn will only recover the incremental cost of changing the nbn™ network technology. As such, the cost of a nbn™ Technology Choice build will be recouped (on a pro-rata basis) where network infrastructure is shared between premises. This will reduce the cost to each premise.

Read more about price adjustments.