It depends on how closely related the sectors are. Two marks can coexist if the goods and services they cover are sufficiently different that consumers are unlikely to confuse the two sources.
The IP office (and any opposing party) will assess whether the marks are confusingly similar and whether the respective goods and services are related enough to create a likelihood of consumer confusion. A mark for software and a mark for restaurant services are unlikely to conflict even if the names are identical; a mark for clothing and a mark for sportswear almost certainly would.
Well-known or famous marks are a partial exception: their owners can sometimes oppose applications in unrelated classes if the new mark would take unfair advantage of or dilute the reputation of the famous mark. This risk applies only to marks with a genuinely significant public profile.