"How safe would that beer be?"

If it's steam coming from a commercial appliance (presumably a dish-washer or some other such food-grade device) it wouldn't be any less safe than eating off a dish that came through it. What you might see is a small carry-over of that plastic-y scent into your beer from residuals left after draining. Unsafe? No. Inappropriate flavor for a beer? Probably.

"...sanitation-water temperature-soaking time for hot tap water?"

An often-cited figure for commercial-grade sanitizing with hot water is 30 minutes at 80-85°C, with an additional 5 minutes per degree C the water used is colder than 80°C. I'm sure this is over-kill for you but it gives you an idea of the heat and length of contact needed for it to be truly effective.

I would think you'd want to at least reach 60°C (140°F) to get some level of sanitizing in a reasonable time (30 min.), but of course this depends entirely on how hot your tap water is. Remember, too, that filling a vessel with water at a certain temperature is not the same as soaking the vessel at that temperature for a specified time, since the water will lose quite a bit of heat as it sits. If 60°C isn't possible, you really won't even approach the effectiveness of chemical sanitizers or proper heat treatment. Note: the above measures (30 min. @ 80°C) should be comparable in effectiveness to properly applied chemical sanitizers, most of which are available to us home-brewers (iodophor, PAA, StarSan).

Below 60°C may still be just fine for your needs, as a combination of good cleaning and the inhospitable environment of fermenting beer may be able to keep infections down. But you're likely to run into issues long term, and learning good sanitation up front is basically the best favor you can do yourself when starting out brewing, so I really don't recommend getting used to using ineffective sanitizing techniques.

"[H]ow high are the odds of wort infection for 1 minutes of 45°C hot water soaking?"

Really depends on the cleanliness of the equipment you're sanitizing, as there might not even be a large microbe load to reduce, but 45°C (113°F) is not likely to do anything in one minute, much less over the course of an hour. It might even serve to incubate microbes (in a moist environment no less) or introduce more microbes (from the water) than were originally present.