Agilent sells a Spice-class simulator as part of its ADS package that can be used on pipelined-ADCs.

It is possible to use their harmonic-balance simulator if you drive the circuits so that they exhibit simple periodic behavior, and doing so would allow you to predict the noise of these types of circuits. But a harmonic balance simulator not well suited to the task. You have to configure it so that is uses a very large number of harmonics, which makes the simulations very slow.

SpectreRF would be a better choice in this case. It employs a time-domain algorithm, and so is much more efficient on these types of circuits.

-Ken