Yep, RF links, wireline (phone company) links, or IP links. All are options.
RF links can be via microwave link, an out of band RF link, just simply having a base radio to connect to the system.
Wireline links are simply a pair or two of wires, often leased from the telephone company, that link the dispatch center to the repeater. They can also multiplex multiple wireline links on to a T-1 circuit.
IP links are just that, internet protocol links between the dispatch center and the radio system. May be a private link or via a local IP carrier.