In order to obtain an Instrument Rating you need to acquire a bunch of things:
a) knowledge;
b) experience;
c) training; and
d) skill.
All of these requirements are outlined in CAR 421.46.
The knowledge can be obtained in a couple of ways -- by yourself, reading material like the AIM and the Instrument Procedures Manual or it could be done through a ground school programme. Transport Canada doesn't care what method you use as long as you pass the INRAT exam. The skill requirement is addressed through the Flight Test.
The experience is gained in a couple of ways -- some of it is acquired on your own and some of it is gained through training. Again, these are all spelled out in 421.46:
(b) Experience
An applicant shall have completed a minimum of:
(i) 50 hours of cross-country flight as pilot-in-command in aeroplanes or helicopters of which 10 hours must be in the appropriate category; and
(ii) 40 hours of instrument time of which a maximum of 20 hours may be instrument ground time. The 40 hours instrument time shall include a minimum of:
(A) 5 hours of dual instrument flight time acquired from the holder of a flight instructor rating ,
(B) 5 hours in aeroplanes where the applicant is applying for a Group 1, 2 or 3 instrument rating or in helicopters where the applicant is applying for a Group 4 instrument rating,
(C) Fifteen (15) hours of dual instrument flight time provided by a qualified person as specified in section 425.21(9); and
(amended 1998/03/23; previous version)
(D) one dual cross-country flight under simulated or actual IMC conditions of a minimum of 100 nautical miles, the flight to be conducted in accordance with an IFR flight plan to include at, two different locations, an instrument approach to minima.
Clearly, the 50 hours PIC Cross-Country is acquired on your own. You also need to have a bunch (40 hours) of instrument time. If you read the article carefully you will notice that only some of this time needs to be dual time. The rest of the time can be acquired through other methods. Namely, with any old safety pilot. The only actual training that is required is the stuff identified as "dual". These are:
a) the five hours from a Flight Instructor;
b) the 15 hours from someone qualified in accordance with 425.21(9); and
c) the 100 NM cross-country flight.
If you are trying to meet any of those three requirements then you need to make sure that they are completed with either a Flight Instructor for a) or with someone that meets the requirements outlined by either Lurch or Bob Sacamano earlier.
425.21 talks about someone that is conducting training towards and Instrument Rating. You do need some training to get an Instrument Rating but you don't need 40 hours or training.
I'm not trying to say that this is the best way to go about doing it -- I'm just saying that it is legal to do what you are proposing.
Take this example:
Person walks off the street and earns their PPL. They do this by flying with an Instructor that does not hold and Instrument Rating. In this process they acquire 5.0 hours of hood time.
The person then moves on to get their CPL. Again, this person flies with a Flight Instructor that does not hold and Instrument Rating. In the process of earning their CPL, this pilot obtains an additional 20.0 hours of hood time. (Let's assume that while building time for the CPL, this pilot also gets at least 50 hours PIC X/C.)
The candidate now has a grand total of 25.0 hours of hood time.
The pilot now decides that he wants to earn an Instrument Rating. He decides to talk to his buddy, an airline pilot that does not hold an Instructor Rating, and convinces him to provide the training for his Instrument Rating.
Our candidate already has:
a) a total of 25.0 hours instrument time; and
b) at least 5.0 hours of instrument time provided by the holder of a Flight Instructor Rating.
All this person needs to do with his Airline Pilot buddy is get an additional 15.0 hours of instrument time (which will include the Cross-Country flight), pass the INRAT and then go do his Flight Test.
(The above example would also work if you replace the Airline pilot friend with an Instructor that holds an Instrument Rating. You could get both your PPL and CPL from a non-instrument rated Instructor and then you still only need 15 hours of hood time with an Instrument Rated instructor to get the Instrument Rating.)
by 3 minutes.