We didn't do this, but we investigated it a bit and learned a few things. My partner tried a few times with a supplementer (the lact-aid is generally thought to be better than the SNS, fyi), but the latch was never right and she wasn't motivated to continue with it. I still remember in the middle of the night hearing her yell from the next room where she was comfort nursing a baby "ow! you do this all the time???" hehe
Anyway, I know lots of two-mom families who have considered doing this and very few (none IRL, 2 online) who have actually done it. This link http://www.fourfriends.com/abrw/
has a lot of great information about inducing lactation without a pregnancy. I do have one friend who tried to pump without using the medication protocol, and she wound up abandoning the effort once the baby was born. Another friend is waiting to adopt and is producing more than 4 oz per day through pumping and the medications (bcps and domperidone).
One thing to think about is the issue of the birthmom establishing a good milk supply. If your friend is going to do this, they might want to consider waiting 6 weeks or more after the birth to start the non-bio mom bfing. It's a tough call, though, because at that age the baby is more likely to have a preference. However, it's important to have the baby at the breast early on to establish biomom's milk supply, as I'm sure you know.
Unfortunately, there are not a lot of LC's who know a lot about this. It's pretty uncharted territory. I live in an area where there are tons of 2-mom families, and the lactation support folks around here still don't have definitive information. And my partner decided not to pursue it largely because of discouraging information from LCs (mostly online). Uncharted territory, but worth charting, IMO. It would have been nice to have an extra set of boobs around here, lol!
Just an aside, why are your friends both doing in vitro (IVF)? Or do you mean that they're doing IUI? I got pg through IVF, but it was because I *couldn't* get (and stay) pregnant through IUI.