I only see your 220 volt circuit, was there supposed to be another one?
But to answer your question (without really answering it), why not use a switch to move the thermistor (electrically) from one circuit to the other? If the two circuits are never operated at the same time, this should be a simple matter. A DPDT switch should be used, with the two thermistor terminals connected to the 2 common leads of the switch. The other four terminals will be going 2 each to your board inputs, with the normally closed pair going to one board and the normally open pair going to the other.
But to answer your question, in a nonspecific way, I do not think it wise to parallel two boards without a means of isolation like with a switch. The circuit impedances of the other board that parallel the thermistor (amplifier inputs, etc) MIGHT effect the overall resistance presented to the amplifier inputs of the other board. This would be bad since a thermistor is a resistance operating device. This is why the switch is a good idea.