News of the merger of the two companies came suddenly yesterday.

Literal

Both-companies [possessive-の] merger [possessive-の] news [subject-が] yesterday suddenly conveyed.

合併 (merger) is standard business vocabulary. 伝わる (to be conveyed/spread) is the intransitive form — the news spread on its own, implying it wasn't officially announced but leaked or circulated. 突然 (suddenly) emphasizes the surprise.