[AnimalMuppet]

If I understand correctly, the initial telephone systems were run by manual operators at a physical switchboard, who could listen in to anything that was said on any line. Many people also had party lines, where someone (in another house or apartment) could pick up their phone and listen to your conversations.

So, no, not much of an expectation of privacy - at least, there shouldn't have been.

[mgbmtl]

If there was no expectation of privacy, the police would not need a warrant to tap a line.