Hi,
There is no reason that a telephone wired for two-wire operation would have the same effect as using Master sockets, I did mention in my post that this may not be too reliable however.
Taken from
here
"Due to limitations of the Renown ringing generator, each extension port effectively has an output REN of 2. Contrary to normal practice, any additional sockets on Renown extensions will need to be Master Jacks to optimise ringer output."
Whilst the above relates to a small electronic PBX, it should still apply to a PSTN line.
I guess I could do a few "home experiments" and see how many telephones I could get to ring using just master sockets
Andrew