Yes, it should work without issue IF you have your network configured properly. Fog works just fine for multiple subnets, even with ProxyDHCP (with minor modifications to base config).
The thing that may trip you up is making sure your layer 3 devices forward dhcp broadcasts from the subnet of the client to the subnet of the DHCP server. Which, should already be setup if you can get a DHCP address on a client in a different subnet.