I decided to conduct a bit of a test, because I was curious about how BoL would work when I was using it on a pally tank and how they would regain mana with their Spiritual Attunement. The way we tested was by having myself, a prot pally, a warrior, and a warlock. The three proceeded to damage themselves by several thousand hp by jumping off of the stairs in Dalaran. The pally tank made himself go out of mana by spamming his abilities. At this point I placed the Beacon on the pally tank and proceeded to heal the warrior and the warlock.
The results were: With all paladin healing spells, the prot pally who was Beaconed received Spiritual Attunement mana from the heal with BoL. One interesting thing that we did discover is that if the holy pally has the glyph of Holy Light the prot pally not only received the mana from the beacon heal, but also the mana from the 10% from the holy light AoE.
Just an interesting thing for pally healers to note when they're healing a pally tank, they can get a little bit extra bang for their buck.