Hay, I just had a stange temptation and I wonder if anyone else has tried it. I own both Battlelore and the Tide of Iron base set (got Toi for dad for x-mas), and I wondered if the terrain tiles were the same size. They are! And they look really great, too. I still prefer the rivers from BL (more to scale), but the hills and woods from Tide of Iron look much more realistic. Plus, many of the tiles are multi-hex, so if they fit into what you need for a scenario, they won't get jostled apart.
And the best thing.........Toi tiles give you both single- and double- hex buildings! Now I can design some custom scenarios where the armies are fighting over a village or town.