Ich has a phase in its lifecycle during which it lives unattached to a fish. During this time it lives in substrate. It is possible that you could transfer an ich infestation from one tank to another if you used live rock from an infected tank.
The safest thing is to not transfer the live rock. If you can make the infected tank fishless for a month, the live rock can be transferred between tanks without fear. Alternatively if you are planning on using the infected tank as a treatment tank, put the live rock (and corals and invertebrates) into a rubbermaid container or another tank while treatment is being done.
