Can my municipal water line siphon from my house water lines?
Yeah, it sounds like you got backsiphoned
Most houses in the US don't have any protection against their municipal water service going negative pressure and backsiphoning any garbage present at outlet points into them.  Even if you have lawn irrigation, the vacuum breaker for that only prevents the irrigation system from contaminating things, not your whole water service.  Likewise with hose bibbs; if your house is recent, your hose bibbs will have vacuum breakers on them, but many older houses lack these, so it was very possible that the contents of your neighbor's kiddie pool or garden sprayer got sucked into the water system.  (Fortunately, most other domestic things have air gaps as part of their installation, but even those aren't foolproof due to the rise of fixtures with extensible heads.)
So, I'd turn off the water heater to avoid heating an empty tank, and make sure to flush your lines and faucets thoroughly once the water's back on, since there's no telling what could have been sucked in during the backsiphonage event.  Also, listen to your water utility, as they may be putting out boil-water orders for a fair length of time after the water comes back on, or even telling you not to use it for drinking if something more...industrial has gotten into the works.