I'm about to start in the ACG grad scheme at ACN but originally wanted to do strat. They told me that everyone was going to be put into the ACG and then streamed, but after doing a bit of asking around it seems that they have streamed strat grads after all....can anyone shed any light on this????

Everyone's in one big bucket. Nobody does Strategy. Some people suck up and get told they're in the "Strategy" stream, but it makes no difference to the work you do and does not even formally get recorded anywhere. It's just a way of stringing ACG along so that the staff turnover isn't any higher than it already is.

not strictly true. majority of grads (80% or there) get put into the ACG. however a small number do get streamed from the onset...a few groups in technology consulting and strategy are definatley streamed..

So when do you find out if you've made it into 'strat'...before you start or in the initial training period??

If you have not mentioned strategy at any stage during the recruitment process, I doubt you would be placed into that area.When i joined (admittedly about a decade ago), you had to explicitly apply for strategy and there was at least one more interview than for all other graduate recruits.

Anon is right. You would have had a 3rd interview to get into Strat. If you didnt have this you won't initially be alligned in Strat. There is a possibility - if during your first 2/3 years you manage to secure strat specific roles, you may be able to move into an alligned domain. But I'm afraid that is pretty unlikely.