What are some good ways to treat frozen vegetables such that they behave like fresh vegetables when stir frying them?

The first thing is to do is thaw them properly before you cook them, half frozen vegetables will cool your pan too much. I often thaw frozen vegetables by soaking them in hot tap water, this is pretty quick and doesn't scorch them like microwaving them might. This might take a bit more time than microwaving but it's a much better result.

You will never get the same result as fresh using frozen vegetables, this is because freezing changes the structure. Water expands when it freezes, rupturing cell walls, which impacts some vegetables more than others. Peas, freeze very well, carrots pretty well. Green beans, broccoli, cauliflower freeze okay, they come out a bit more limp than fresh. Thin leafy vegetables like spinach don't freeze well at all, they come out very limp, almost as if they're cooked already. This isn't a deal-breaker, just something to be aware of. On the rare occasions I use frozen spinach I will squeeze the hell out of it after thawing as it's water-logged.

Cooking order will be important to sauteing them successfully. Water is the enemy of getting color on your vegetables, so you want to make sure they are relatively dry before you add them. Hardest vegetables go in first, like carrots, then medium ones like beans and broccoli, last you add the leaves because they take the shortest to cook and will give off a lot of water no matter how well you wrung them. You want the vegetables to be mostly cooked by the time you put the spinach in as the water will put an end to any browning. Peas go in last, they only need to be warmed through.

If you don't feel like waiting for them to thaw, you can submerge the bag in hot water like @GdD mentioned.

I prefer steaming frozen vegetables however. The trick is properly steaming them though.

I love using the frozen steamables, I just pop them in the microwave for the set time and they're always cooked perfectly. But if the bag of frozen veggies isn't in a "steamable" bag, then you can grab a glass bowl (like the pyrex storage containers) and put a tiny bit of water at the bottom and dump the veggies in it. Next, put the lid over it and seal it except for one section so steam can escape and microwave it for 4:30-5 min. If the veggies seem very frosty, then don't put any water in it because it melts sufficiently. When I do this, the veggies always come out perfectly/evenly cooked (not too hard or soft).

But if you like to stir-fry, just toss them in the stir fry after to get some quick color to them. Or steam it for slightly less time so it can stay on the stove longer without becoming over-cooked. Steaming vegetables cooks things pretty evenly, so I think it'd be your best bet. Its just steaming means the container needs to be sealed enough to keep the pressure, but have a super small gap somewhere to let it escape when it builds too much.