depends on what other tomaotes are nearby wind is your big pollenator with tomatoes bees do not do much for them. but you have to issolate and there are many methods to employe cages work well with a good screen to kkep insects and bees out

Actually tomatoes are a self pollinated plant, not wind pollinated-and bees will do the pollination on the potato leafed types like Brandywine.

I have not grown them (I though Bonnie's Best was the name of the greenhouse company that supplies the plants to Wal-Mart and other box stores and spread late blight throughout the eastern USA) but id they are an heirloom and you have at least 10' between the varieties you should be okay. I save a lot of tomato seeds ever year and rarely have crossing, though when I do a potato leaf variety is always involved. the rule of thumb is plant a block of at least 8 plants and 25' of separation between the varieties. Tomatoes do not need a lot of isolation.

Even if the BB tomato is a hybrid you can still grow out the seeds, they just won't be like the parent plant (well a few should be, but most won't)

You should read the book Seed to Seed by Susan Ashworth

Hubby found a "Bonny's Best" as a heirloom, spelled differently that Bonnie's Plant Farm's plants.

I got mine at Millington seeds,
My plants look nice 4inches and potting on to bigger pots today....
PP

Bonny Best/Bonny's Best supposedly introduced very early in the 20th century. A commercial variety, noted as being slighly later than Earlianna, round,red and baseball size. Noted as a canning tomato, but used for other purposes as well. Indeterminate. Burpee stated that it was a selection from Chalk's Early Jewel. Widely available.

Bonnie's Best is an heirloom introduced in 1908 by a nursery in Union Springs, Alabama. Cross pollination rates are generally 2 to 5 percent unless you bag the blossoms, use shields etc. Normally, I would not worry about doing any of that unless you were going to sell the seed. In this case you may consider trying to keep some pure seed since this tomato is becoming rare.