"An undertaking which occupies a dominant position in the provision of an essential facility and itself uses that facility (i. e. a facility or infrastructure, without access to which competitors cannot provide services to their customers), and which refuses other companies access to that facility without objective justification or grants access to competitors only on terms less favourable than those which it gives its own services, infringes Article 106 if the other conditions of that Article are met (cf commission document). An undertaking in a dominant position may not discriminate in favour of its own activities in a related market. The owner of an essential facility which uses its power in one market in order to protect or strengthen its position in another related market, in particular, by refusing to grant access to a competitor, or by granting access on less favourable terms than those of its own services, and thus imposing a competitive disadvantage on its competitor, infringes Article 106." © Commission Decision of 21 December 1993 relating to a proceeding pursuant to Article 86 of the EC Treaty
On this topic, see the following e-Competitions special issues:
"Transport & Access to facilities: An overview of EU and national case law"
"Access to facilities in the energy sector: An overview of EU and national case law"
"Access to facilities in the telecommunication sector: An overview of EU and national case law"
See also Essential Facility