Bella WAS potty pad trained, but we switched to outdoor training because....
She was ONLY consistent at home. Anytime we went to anyone else's home, it was definitely hit or miss. We'd go one place and she would do AMAZING, then we'd go another and she didn't use it once (all accidents!!)

As you can imagine, I AND the person whose house it was hated that (even though I always travel with pet odor/stain spray)!! Also, Bella marks, which is totally different than peeing, and if you watch closely you can tell which it is. Because of that we decided to retrain her to potty outdoors. Now, she's about 98-99% everywhere we go including home! Yay!!
I believe that a lot of her potty pad issues had to do with simply getting confused. The places she had accidents were places other dogs were, so it's my feeling that those places had scents (other accidents, marks, ???) that confused her.
She pees 3-5 times a day and poops 1-2 times a day (usually at the same time she's peeing, but not always--sometimes it's a separate trip, which is probably my fault because I didn't wait long enough before going back in).
Also, I should probably say that I have a yard but it isn't fenced. Therefore, all our potty trips are leashed walks around the yard. She has gotten VERY good about quickly doing her business and going back in. Probably because we didn't give her long from the beginning. If she didn't go right away, we went back in. Buuut, after she goes, we try not to take her right back in, unless she's headed there on her own. That's probably another reason she doesn't take forever....she doesn't associate "going" with having to go back inside.
Good luck! I have found that Bella pees in other people's homes it seems like because she smells other accidents, marks, excited pees, something?? If your friend's dog is peeing outside and then coming right back in and peeing in your house, that sounds a lot like marking to me. Marking is instinctual and is VERY hard if not impossible to stop. Bella doesn't mark as much because she got in trouble EVERY time she peed OR marked. Maybe she's just gotten out of the habit of it??? As far as your friend's Yorkie not wanting to have anything to do with your toy poodle.....Bella is that way sometimes with puppies, even older puppies. I don't know what it is about them, but their just to spazzy for her or something. I don't know how old your dog is, but maybe that's it??