The OpenSprinkler unit is quite small compared to classic timer boxes therefore there should be plenty of room in a typical enclosure to fit all the items. With that said, the outlet is typically in a corner so plugging in two bulky items might be difficult.
If this is the case, you can use a simple extension on either power adapter so move the bulky box item elsewhere in the enclosure. Please note the power line adapter cannot have a surge protector in its path as those typically filter the frequency used for the network. A classic extension cable will work without issues though.