"The observers’ findings, which have been endorsed by the European Union and the United States, essentially legitimize the transfer of power from outgoing President Robert Kocharian to his longtime chief lieutenant in the eyes of the international community. The West and the United States in particular are clearly unwilling to undercut Armenia’s two top leaders, who seem to have agreed to a resolution of the Karabakh conflict proposed by the U.S., French, and Russian mediators. During their most recent trip to Yerevan and Baku in January, the three co-chairs of the OSCE Minsk Group came away from their talks with Kocharian quite satisfied. (Ironically, Kocharian and Sarkisian had forced Ter-Petrosian to step down in 1998 for advocating essentially the same peace deal.)"
If this is the case, then the OSCE has lost a lot of credibility as a credible monitor. I still think it possible the government was simply able to avoid the monitors in some fashion.