- "The telegraph office was in operation since June 1879"
In BrE this is not correct. If the telegraph office is still in operation, you could use the present perfect here. If not you should use 'from' not 'since'.
bhaisahab,
Thank you for specifying that point!
Does it mean that 'from' must be used also in cases when we briefly report on past events whose end date (completion date) is not specified. For example 'John Smith became a member of the Liberal Party from 1859'?
Does it sound naturally or we just need to use another pattern (construction) in order to express the same idea?