New York City residents finally are digging out of a devastating post-Christmas blizzard, aided by unexpectedly warmer weather. But a growing number are sounding as if they want to use their shovels against union snowplow workers and their supervisors. Various news outlets have reported that leaders of the Service Employees-affiliated Sanitation Officers Association ordered their Teamsters-affiliated work crews to slack off as a protest against recent City Department of Sanitation budget cuts and demotions. The apparent work slowdown not only paralyzed traffic, but also led to two deaths and any number of commuters trapped overnight in subway cars. On the hot seat, Mayor Michael Bloomberg has demanded, and is getting, a full investigation. Union leaders deny culpability, insisting fiscal austerity had reduced manpower. But evidence appears to undercut such claims.