Wow. 2 years FM and 1 year EM and be certified in both? That seems kinda crazy. I am not sure 2 years would be enough (for me) to be comfortable in FM, let alone being comfortable in EM after 1 year. 1 year! And then you may be the sole attending somewhere with a difficult airway, or a trauma, or a very sick septic patient or just someone you don't quite know what to do with...
Fortunately, I got a lot of experience with this scenario in my residency since I did a 4 month stretch in a remote hospital up north. After my 1st month I did call on my own with the attending a 20 minute drive away (if the roads were good); I could call for help if I got into trouble (and sometimes the nurses would call anticipating trouble) but I always knew I was on my own for the 1st 20 minutes or more if the doc wasn't there when I got there. I also did 4 rotations through the ED and one through anaesthetics to prepare for what awaited after residency (I used all my electives for either EM or gas).
As an attending I worked in one of the shops with double cover for the 1st couple of months so I was able to ask qustions if I wasn't sure what to do. Our guys are very supportive of each other and even the guys with 20+ years experience will sometimes talk over a case before making a decision, so answering noobs' questions is seen as an extension of that professional courtesy. I also did my 1st FP locum in a group practice and would occasionally walk down the hallway to ask one of the other docs what to do. I still occasionally leave a note for my partner asking for advice (he's been in practice for over 40 years so hasn't reciprocated yet).
My 1st night as a single cover attending (in an emerg a good 20 minutes away from the regional centre by ambulance - if you can get an ambulance) was a little scarey, and there are some things that still make my pulse race, but we have pretty good back-up here and my residency prepared me well for what I was going into. Our docs are also pretty good at teaching on the job, and I have done a lot of extra CME since I finished to cover some of the gaps in my knowledge base. Oh, and our chief gave me his cell number and told me to call him day or night if I didn't know what to do and needed advice. I never used the number, but it made me feel better having it and permission to wake him up in the middle of the night (or day).
As to why people do the 5 year program, if you are sure you want EM, the 5 year EM residency is a surer path if you get it. You know from the start that you have the EM training you need. If you do FP, you may or may not match into a 3rd year EM program as there are few spots and they are highly competitive. If you don't get one of these spots your options are to work for a year and try again or give up (or, if you work in an odd shop like mine in an out of the way province that is seriously resource poor, work EM anyway). There is also a perception that if you want to work in an academic setting you should do the 5 year program, and I have heard med students say that they thought in time the 2+1 program people would be disadvantaged (i.e. not allowed to work in high acuity settings). I used to worry about that but I've stopped giving it any thought at all. Unless we have a serious surplus of docs in Canada in my lifetime I have job security, and I can't really see that happening.
Sorry this is so long. Y'all know I babble when I'm tired. Cheers,
M