Pretty sure you could.
The first network I set up in my original studio apartment was PhoneNet (CompSpewSA was having a sale on Belkin PhoneNet boxes at the time). It connected a IIgs, a IIsi and an SE/30. The IIgs netbooted, verrrry slowly, off the SE/30. Pretty neat at the time.
I still have a PhoneNet segment in the house. In fact, it was easier to network the 486 games PC with a LocalTalk ISA card! A Dayna EtherTalk bridge wires it to the other Macs and fileservers on the 10Mbps segment. I still have to set up my Shiva FastPath.