Soviet Union built many systems with Digital Equipment Corporation's PDP-11 ISA -- some were straight-up clones of PDP-11 models, down to the chipset, others reimplemented the architecture -- see http://www.dbit.com/pub/pdp11/faq/faq.pages/Soviet11s.html for background information. They were used much like the originals -- for timesharing, industrial process control, data acquisition and so on, including personal computing and embedded use.
Out of all PDP-11 processor variants, MAME currently emulates only T-11 single-chip CPU, intended for embedded applications. DEC VT240 terminal (and its clone, Elektronika MS 7105) uses it, along with another Elektronika system, MS 0515 -- an unusual choice for a desktop. MAME emulates both of them. Other professional PCs (DVK series), educational machine (UK-NC aka Elektronika MS 0511) and home computers (BK-001x series) used K1801 chipset, which is not emulated.
However, it is possible to use MAME as a terminal emulator connected to a simulated PDP-11 running in SIMH. As an example of this, the linked guide shows how to install RT-11 operating system in a simulated PDP 11/23.
Elektronika MS 0515
A rather obscure machine, possibly intended as educational or gaming system -- video memory layout is clearly inspired by ZX Spectrum, and a few ports of Spectrum games exist. Was designed and built by the "Processor" firm in Voronezh (same place that produced many other PDP-11 clones).
MAME driver name is ms0515. Hardware emulation is not 100% complete, but enough to boot the operating systems (OSA and Omega, a/k/a modified DEC RT-11) and run the games:
Saboteur 2 port
Stop the Express port