there will be no difference anymore between LH and SH - you will all be trained in the same groundschools on all three aircraft (A320, 321, 330)
You will then be given either primarially LH flying, or SH, but your roster could include a mix. The reason they might of told you for a SH interview that you could be doing LH flying is that you are able to work LH hours, which means they can call you out or roster you for a LH flight if they wish, so yes if you are TJQ SH you probably will do some LH flying and vice versa.
all one groundschool. no difference anymore.