How does an Active RFID transponder tag get activated?
The tag is not activated by just any RF signal, even one transmitting on the tag's preassigned frequency. The tag receives an RF signal that has certain information encoded in it. If the RF frequency is within the tag's preassigned frequency, and the received signal contains a code that matches the tag's preassigned "turn on" code, then the tag will in turn transmit it's data.

The chances that a random wifi signal will match both the frequency and codeword requirements of any given tag are vanishingly small. By design.