I assume in the same manner we do with theirs when they leave port.
Something to keep in mind... There are rumors from the Russians having some capability to use satellites in sub detection. Whether that uses radiation or heat signatures or wake detection or wildlife effects, I have no clue. The Russians brag a lot and hopefully that is an exaggeration. The point is there may be a breakthrough in sub detection some day.
One thing is for sure. If we dismantle our ICBMs the Russians will have close to 1000 newly free warheads to use for SSBN fishing... and once the first SLBM is fired from the sub that subs position is known (I assume the Russians have the same missile launch detection satellites we do)
Tough to do when the attack sub isn't as quiet as ours are. While not impossible, I know of no instance when we were able to track our own boomers.