本港長途電話供應商是何種市場結構?

是的,是寡頭壟斷,oligopoly.

壟斷的門檻是網絡資源,如用租的,要與網絡架設者合作,如果是自設的,門檻的投資額.

這種生意,不是百萬元便可創業的小本生意.

行業內的競爭性自然只局限於幾間.

In the past, HK mobile service is OLIGOPOLY.
Under Oligopoly market, there are few sellers and many buyers.

But now this industry is changing, some competitors enter into this market. Besides, there are some sophisticated subsititues, e.g SKYPE.