Extrapolating from the general sad state of the weapon systems in use by Russians where they are at this point unpacking tanks made in 1950, the quality of maintenance on their vehicles, and is difficult to plausibly claim that all the ancient rusty USSR stuff across the strategic rocket barrier is in any sort of usable shape.
Now, if an order to launch is given, some rockets may launch, some of those may actually fly, some of those flying actually get somewhere, and perhaps some of THOSE may actually detonate should they reach the target, and maybe if you're lucky at the designed yield. The percentages in that funnel that aren't known. And nobody [perhaps except some crazies] wants to find them out because even one in the middle of big city is enough.