Side impact airbags are certainly not reusable in any vehicle where any airbags have deployed. The key reason they are not reusable is that if the front airbags and possibly the roof curtain airbags have deployed, it is almost a certainty that the side airbags have also deployed. Once any airbag has been deployed, it is not reusable. Even if only one airbag in a vehicle had deployed, it is still a good idea to ensure that all airbags are new. You will never know if the deployment mechanism that triggered the original deployment is working correctly. In other words, don’t take any chances with airbags and replace them.
For more info, see The Dangers of Car Airbags