I guess it could mean that they got approval to operate on 453.35 conventionally in the event that whole specific site was down. My understanding is that if a controller goes out and there is nothing to control trunking, radios could actually communicate on one or more of the frequencies in repeated mode sans a controller. So, there would be full operation, site trunking (no connectivity to the SIRN network), or total loss of trunking [but still have individual repeaters available and specific radios set up in a way tht the radios are designated a repeater frequency where they could still operate conventionally.
Remember, all of the radios transmit a NAC. And each frequency actively part of the site is a repeater. So if all trunking mechanisms fail, there is the possiblity of still using each of those frequency pairs in a repeated mode, and that each repeater [when not actively part of the trunked system] would respond to transmissions with that NAC on the input by retransmitting the audio on the output just like any normal repeater.
Mike