All the employees agreed that the new regulations had __________ positive changes in the workplace.

The sentence describes employees unanimously recognising that new regulations had caused beneficial changes in their work environment. The blank requires a phrasal verb meaning to cause something to happen or to introduce changes.

"Brought about" (Option A) is a phrasal verb that means to cause something to occur, perfectly matching the context of regulations resulting in positive workplace changes. 

The other options convey different meanings, and are therefore unsuitable: "brought on" (Option B) typically refers to causing something negative like illness or trouble; "brought along" (Option C) means to bring someone/something with you physically; and "brought up" (Option D) usually means to raise a topic or to raise children.

Therefore, Option A stands as the only phrase that properly preserves both the grammatical structure and intended meaning of employees acknowledging policy-driven progress, making it the correct choice here.