Can I use Back in Stock with apps such as Quantity Breaks?

Yes, Back in Stock works with Shopify apps such as  Quantity Breaks from Bold Apps.

Quantity Breaks is used to create tiered pricing, or discounts, for customers wishing to purchase multiples of a specific product variant. Quantity Breaks works by creating additional product variants with the adjusted price tiers. Here's an example:

In the table above the first product variant is the original item. Quantity Breaks has created an additional variant with a reduced price for customer wishing to purchase 10 or more. As long as the product inventory is managed through the first, original product variant Back in Stock will record and send customer notifications as usual. 

Exclude the variants created by Quantity Breaks from the Back in Stock popup form

To ensure customers only sign up for a Back in Stock notification on the first, original product variant you should exclude the additional variants from the popup form.

1. From your Back in Stock dashboard choose Customize, Popup form
2. Find the checkbox for Hide duplicated variants with the same SKU and turn it on
3. Hit Save form settings

The Back in Stock popup form will now only include the first product variant that exists for each SKU.

Note: If you are using an custom form in your product page, or an integration for Out of the Sandbox themes that includes the form in the product page, this option will have no effect. It can only filter the variants shown in the Back in Stock popup form.