I don't see the point in the IRS running TurboTax themselves. The IRS should simply keep track of everyone's taxes and automatically send refunds or bills accordingly. Spend any extra money they have on auditing the rich.
But that seems like more steps than you'd need. The IRS already must have the ability to fill in everyone's tax returns, because they're able to calculate what nearly everyone owes, pretty accurately. Since tax returns are basically "follow the instructions and fill in boxes so that you can eventually get a final number", then that must mean that the IRS can already do that.