Help with centralised and decentralised structures please?

If a company has two branches both with a managing director and senior managers for the production, sales, personnel and research, is this a centralised or decentralised structure? If the two senior management teams are combined into one at a new head office between the two, is this now centralised or decentralised? Also is it flat or tall now, and which was it before? I'm very confused and would appreciate any help

Decentralization: Organisation along strictly hierarchiat model. No delegation of authority is permitted. Centralization's benefits of clear direction and facilitated planing are offset by its inflexibility as well as poor accountability since no subunit has independent authority to act. No other agency has responsibilities of central planning; this limits communication and spontaneity but has the the advantage that all organizational activities are more easily coordinated.

Decentralization: Essential decision making and policy formulation done at several locations throughout an organization. The objective is to give decision making authority to those most directly responsible for the outcome of those decisions, with first hand experience and knowledge about the issues involved.