Never heard of anyone doing it that way. I don't see why it couldn't be done. Just make/buy the tubing a little bigger than the fitting its connecting to and put some kind of sealant around it and let it set. Thats how I would see it being done. I used a .25"....I guess it was nylon, latex, plastic.....hose to a "T" into the MAP line. I accidently hit it with some penetrating lube spray when I was spraying where the down pipe clamps to the turbo. It started blowing off after that untill I put a hose clamp on it.
Only problem I could see for the copper tubing is it may be a little more difficult to run (especially under the dash and up the pillar). It would be a tight bend behind the gauge and may crease
I'd have to get a piece and play with it to see how it acts when being bent.