Yes, 10.8V and 11.1V battery packs are interchangeable.
Battery packs are built by connecting individual cells in series and parallel. A battery voltage rating is calculated by multiplying number of cells in series with number 3.6V or 3.7V. For all practical purpose, there is no difference between individual cells rated at 3.6V or 3.7V. Some manufactures picked 3.6V while others used 3.7V for the same type of cell.
This explains that there is no difference between batteries rated at 10.8V and 11.1V, same is true for 14.4V and 14.8V battery packs.