Taiwan's BLs do love a good crossover. But they also love a good open-to-interpretation cameo. As well as a good passive reference.
Even Plus & Minus's were up to interpretation because the couple from Be Loved In House were never named in the script, the credits, or in promo materials for their presence (unless I missed something somewhere, which is possible considering what they are called in the MDL cast list).
And the main CP from HIStory 3 shows up everywhere - sometimes named as someone different, sometime unnamed (and thus open to interpretation).
In Be Loved in House, we get a character who's dialogue references the fact that he and the ML shared a previous drama together, despite the ML being a different character in Be Loved In House.
You can also often see BL posters from all over the world on the wall, in trashbins, etc. I think someone even spotted a BL poster from another Taiwanese BL once. But I cant remember what.