No, Sherlock gave them a Victorian look, and changed some other details, but their roles are pretty much exactly the same as in real life.   Even to the extent that putting Molly in the same role is a clue. 

If Mycroft had employed Mary, I doubt they'd have spent a lot of time working together in the same room - they might have met for a briefing.  And he wouldn't have employed her to access top level security.  He could have done that himself. 

It's putting those two unexpected things together - Mycroft being aware of Mary, and Sherlock imagining she worked for him.   It's not conclusive, but it's a very strong hint, and I don't see anything that contradicts it. 

And this is a meta about the "unreality/reality" of the first plane scene - very convincing:

http://thevanishingtwin.tumblr.com/post/136609775862/is-the-first-plane-scene-real

This is not really making me any happier. 
If we suppose the first scene is MP, Mary announcing in this on the plane might hint at her reading Sherlock like an open book, knowing when he’s fibbing, his feelings being transparent to her at all times. 

Well, that does make a lot of sense.  And eve left-handed people who were forced to write with their other hand still feel more comfortable using their left hand, so it would make sense that when he's not writing he would spontaneously use his left hand for other things.  

I hadn't noticed that though, so good observation from whoever caught that.

Interesting detail indeed. Is Martin left-handed?

He definitely is. In the 1940s and early 50s my mother-in-law was still forced to use the right hand. One generation later I was allowed to write as I wished but one teacher kept nagging me about it. 

I love their attention to detail! 

But I feel awful for those people who were raised that way. I remember in school they once told us to write with the 'wrong' hand for a day. Only for a day, and I hated that. I can't imagine being treated like that all the time! 

Same in Norway, people were forced to use their right-hand. It wasn't that long ago, it makes me wonder if Martin experienced the same in school.

I would hope Martin was a bit young for that treatment, but I could be wrong.
Doesn't bear thinking about...

besleybean wrote:

Such ignorance is awful and pure child abuse!

At the time they thought it was necessary. And you know, today we still live in a right-handed dominated world. I have a left-handed son. 35 years ago, in 1st grade, his teacher thought he was "slow" because he couldn't for the life of him use scissors when it was time to do crafts. Come find out, all he needed was a pair of left-handed scissors, and once he had that, voila!  He was no longer deemed slow. It's a tough world out there. He told me recently that he's forced himself to learn to do some common things (like use scissors) right-handed, out of sheer necessity.