schwarcz, I am not sure exactly what you are looking for. Vanguard Asset Management Services (VAMS) is not in the business of actively managing or trading a portfolio. The actual portfolio is selected by you with advice from VAMS - accounting for existing holdings, desired allocation, the purpose of the portfolio, etc. There are probably thousands of different portfolios with both additions and withdrawals, so I have no idea how Vanguard could provide a meaningful IRR. You do get quarterly reports however, and they probably look much like any of the Vanguard quartlerly reports - no IRR.
After a short conversation with VAMS several years ago, I got the impression that, aside from advice and a shoulder to lean on, their function was largely mechanical - making sure dividends go where you want them to, making sure RMDs are taken, rebalancing as required, and attempting to minimize taxes.
If my #2 son does not want to manage the family portfolio after my passing, VAMS is the fall back position. Along with the application form, my wife is instructed to send along a copy of our Investment Policy Statement.
Volatility is my friend