Variable valve train control works without feedback, but many say it works poorly. So you could control it with a simply 2d table of "dutycycle vs rpm", but results are not exact, that's why you have the complex signal feedback from trigger wheels on the cams.
To know how the engine works without the VVT you would have to figure out what the default setting for the cams are when the solenoids that control it are turned "off" (not controlled by ECU). There is usually a "limp-home" mode, with BMW people often lock the cams and disable VANOS which results in a high power mode, and a small loss of low-end torque. If you turbo the engine this is rarely a problem since you already have enough torque.
