NTC to multiple inputs
Can I simply tap the two wires and connect them to the fan controller without affecting accuracy?


No, you cannot.

A thermister is a variable resistance. In order to read its value, a controller must send a current through the thermister and measure the resulting voltage across it (or something equivalent to that).

Therefore, if you connect one thermister to two different controllers, each one will be trying to apply current, and you'll end up with twice the intended current through the device and twice the voltage, which will give a completely wrong temperature reading.

In order to do this correctly, you need to allow one of the controllers to function normally, and then buffer the resulting voltage for the second controller, taking into account the fact that the second controller might be using a different value for its sense current, which would require the voltage to be scaled accordingly. The current might not be a constant value, as well.

One or both controllers might not even have one end of the thermister connected to ground (or any other shareable reference node), further complicating matters.

In other words, you need to know a lot about how both controllers work internally before you can consider how to get them to share a sensor.