A separate broadcast makes much more sense on the complexity front... if it were tied to the cache, the TLB wouldn't really care about anything other than specific transitions. It doesn't need the cacheline contents, and one cacheline would generally hold 8 or 16 PTEs (depending on PTE and cacheline size.) You'd also necessarily be binding to the PTE's physical address since page table walks occur on physical addresses.

With a broadcast, on the other hand, you get the specific transition event you need, and you can choose whether to broadcast the physical PTE, physical data or virtual (+ASID) address, or both. You can also have an acknowledgement returned if needed.