I heard "près" (which seemed logical enough) in place of "prêts"; is there a difference in pronunciation between the two?
Nope there is unfortunately no difference between "è", "ê" and "e" followed by a double consonant.
You can't finish a sentence in french on a preposition, if it was to be PRES, it would have to have ended like: ils aurions été près de nous.
But also no reason why it couldn't have been - "We could have been near/close." Yes?
When the noun is masculine, they are identical in sound but when the noun is feminine, prêt becomes prête and then you pronounce the T at the end.
I might be crazy but I think when people speak this there is about 1/3 of a T at the end. It might be geographical (Québec) though. also I think the vowel is slightly different. the è being a little farther back in the mouth ( not that that's easy to hear)
plus the "près" would be "proche" would it not?
I think you're right it's regional, in Québec the pronunciation is very different (even the vocabulary is) than in France and they might pronounce the T. But done in France there would be a confusion, as "prêT" sounds too much like "prête", wich is feminine for "prêt".
According to Wikipedia, the opposite is true for Québec French pronunciation: The t is not even pronounced in words such as correct, reste, ministre(!), texte.
As you are no doubt exposed to a lot of European French, this might create an equivalence in your mind between the pronunciations with and without t, so that you hear the t even when it is not spoken. These equivalences operate on a very low level and are unconscious. (They are also to blame when English r and French j are very different sounds to us, whereas in fact they are extremely close and the Chinese sound written r in Pinyin is somewhere in between and sounds sometimes like the one to us and sometimes like the other.)
What I hear, here in Canada, is almost a glottal stop after the vowel, the "è" is chopped quite short without the "t" actually being pronounced at all.