The morning of the confrontation, the scene starts out with both of them behind the back of Ennis's horse trailor, no doubt settling thm in for the ride home, but I see Ennis wiping his mouth before he picks up Jack's saddle, A sloppy goodbye kiss from Jack?....
btw, I don't recall Jack owning a horse of his own, and he owns a saddle? Anyway the horses saw and heard it all did'nt they? Best seat in the house, like a fly on the wall so to speak.
I also see a rifle and various other items belonging to Jack, but no fishing pole. Hey Lureen, guess what! Did'nt she have a clue? And later on, " Husbands don't ever wanna to dance with their wives", "Why is that Jack"? I hear a suspicious taunt, but maybe I'm wrong. Hmmmm telling? Just a few observations of mine. Thanks.
I also noticed Ennis was quick to help Jack with heavy lifting, like the man usually does. I think this settles the question of who is which role.

In the short story, I think the horse trailers is also on Jack's truck, but it makes more sense for Ennis. 14 hours with horses on a trailer is torture in the summer. Jack is rich enough to own his own saddle and horses, too. But I think Ennis always provides the horses and some of the non-perishables, while Jack always bring the food, beer, etc. Like the time after the reunion, Ennis was late, Jack was already peeling potatoes and putting them into the pot, like that time in '63 when Ennis came back after his first night out, and washed everywhere he could reach.
I think on the phone with Ennis, Lureen said something about "fishing buddy or hunting buddy, I knew that" so she wasn't sure or cared about what they did up there. She still suspected something. When Ennis said they herded sheep in Brokeback one summer in '63, and that Jack's favorite place was Brokeback, but never told her about Ennis and their twenty year friendship/relationship, she KNEW the reason Jack's long drives two three times each year, and all his drinking and lack of romance. She teared up real quick, but caught her composure to tell Ennis to go visit Lightning Flat. Then she hung up real cold and fast. Ennis was caught off guard. Anne Hathaway is such an amazing actress to bring out the charm and pain of Lureen. I like that better than the cold character in the short story. She also suffered so much, without the shock and trauma of what Alma went through. Their song is "No one loves you like I do" and Jack is certainly not loving her like any man. The irony must be a painful reminder every time they want to dance. Maybe THAT's why they never dance. Jack is reminded of the loneliness without Ennis, and Lureen is reminded of a husband who is inattentive or worse. I think she buries her love for Jack in the books, in the business to remind herself that he wasn't a mistake. She still loves him, as can be seen in the Thanksgiving scene. She also looked at him lovingly when their child was born. Jack was just too insecure at that time to stand up to old Newsome. Instead he went and sent the first postcard to Ennis. I guess in a way we have old Newsome to thank for the movie. Without him, Jack would never be driven back to Ennis' loving arms. He may play the loving father all his life, keeping the two shirts secret with only Jack's Ma knowing. Naw...Jack would've send that postcard sooner or later. Love is a force of nature. And every year when he visits Lightning Flat, the reminder will be there.