"I wanted to know if it is possible to join a different business stream if you don't like audit after a year or so. For example are there opportunities to move into Consulting or Financial Advisory? Also how closely do you work with other business streams, and do you end up having good working knowledge of what exactly they do?"
Question 1 - If you don't like audit after a year or so, you'll just join many of the disgruntled associates who end up staying in audit for some more time. The way it's set up, you can only really transfer into other non-audit groups after 4-5 years in audit. As far as consulting goes, consider Deloitte, since the other 3 firms spun off their consulting groups after the whole Enron scandal. The other groups have an implicit understanding with their audit brethren so they don't steal employees within a year or two after they join. Put the time in and you have a better shot. There are exceptions, and they'll try to sell you on it, but this is the general reality.
Question 2 - We do have a working knowledge of what they do, and we only really work with groups that independently verify certain valuations made by the Company. Private companies, for example, value their common stock every year or two. Since these stock valuations affect stock compensation expense, we obtain their valuations and provide it to our valuations specialist to independently verify the assumptions and calculations. Other groups we usually use are real estate valuation specialists, derivatives specialists and intangibles specialists.