In southern Russia you may use an Inmarsat phone, for total Russia is basically an Iridium phone the right choice.
Using BGAN in Russia:
Depending on to which Service Provider a BGAN SIM card belong to it is not unrestrictedly usable. As our knowledge onlySIM cards from the Service Provider MVS are working without any restriction. Ask your Service Provider about the usage in Russia or directly ask us about a MVS SIM, we offer these SIMs as well.
Using Iridium in Russia:
In order for a subscriber to comply with Russian regulations for the use of Iridium mobile satellite service in the territory of the Russian Federation, online subscriber registration is necessary for all subscribers located in or traveling to Russia. The process for registration is simple, and can be completed at: www.iridium-russia.com. Note that subscribers are able to register their device for use in the territory of the Russian Federation prior to their arrival in the region.
Information from March 2018. Source: Allan&Associates (no longer available)
Bringing satellite telephones into Russia requires require advance approval from the Russian telecommunications agency Roskomnadzor, according to a report by the U.S. Department of State Overseas Security Advisory Council (OSAC).