As from 1 January 2017 Switzerland is associated to the entire Horizon 2020. In practical terms this means that for all Horizon 2020 projects for which the GA is signed as from 1 January the Swiss participants are automatically eligible for funding and may count towards the minimum number of participants required for a project (see the eligibility criteria for funding and participation under Regulation 1290/2013 on Horizon 2020 Rules for participation).
For more information, please consult: http://ec.europa.eu/research/participants/data/ref/h2020/other/hi/h2020-hi-swiss-part_en.pdf