With a PoD butterflying Watergate and Belenko's Mig-25 flight, have the original B-1 design move ahead. The B-2 isn't ordered as early, the B-1 isn't cancelled in favour of upgrading B-52's, and there's a larger initial order.
The price of the airframe comes down and it could be in economic reach of Britain. Political reach, I don't know.
Considering one of the books about the B-1 is called "
B-1 Lancer: The Most Complicated Warplane Ever Developed" I doubt price is going to go down much.

Not even if the US orders the original 240 B-1A's. Apart from purchasing especially the upkeep is going to be horrendous for a strategic bomber as the B-1, especially for a non-US military in small numbers.
Wiki mentions a price for the B-1A starting at 40 mln USD in 1970 but escalating to 70 mln USD in 1975. Unfortunately the program was still in prototype stage by then and later costincreases were likely, even
Apparently the latter number amounts to a share of the GDP comparable to
645 mln USD in 2012.
I doubt the B-1 is in economic range of Australia or Canada. It's also outside of Britain's reach unless the BAOR and f.ex. the ASW focus in the North Atlantic go.
I would have loved to see the B-1 in RAF service. It would have worked as a replacement for the Vulcan. That being said there were one giant issue with it, price per unit. If the price was cut but a large amount then I could see RAF looking a picking up some. Canada might look to a very small number 3~6 for a northern strike capacity, as there would be such a small number, the US would be very involved in keeping them flying at a lower cost. Australia might pick up the same amount.
One idea is that Rockwell designs an "export" model that is not designed to carry a nuclear payload but is designed around a high speed anti-shipping missile.
Developing an extra version is going to increase cost yet more. Worse, the US didn't need or want a conventional bombing version untill the '90s, so that would mean the other operators would have to pick up the tap for that, as in the UAE and the F-16 Block 60.
Owning 3-6 aircraft means no more then 1-3 are operational at any one time. That doesn't make much sense IMHO.
Besides the previous poster made much sense; the RCAF already operates 21 CP-140 Aurora's, which can easily be adapted to fire Harpoons for a pittance.