Further testing required, however this may be caused not by having multiple Expert Masonry improvements, but rather by the Spyglass Overlook structure. During play last night, I experimented building fresh towers under the influence of multiple buffs, and discovered that any building that was in the spyglass's radius would be ignored by the masonry afterward, even if I then deconstructed the spyglass.
MCLG-133
Try Redstone Launcher + Spyglass
Further testing required, however this may be caused not by having multiple Expert Masonry improvements, but rather by the Spyglass Overlook structure. During play last night, I experimented building fresh towers under the influence of multiple buffs, and discovered that any building that was in the spyglass's radius would be ignored by the masonry afterward, even if I then deconstructed the spyglass.