Paraphrase, e.g.: >>Our team is ready anytime for swift action to meet your needs in special, challenging situations<<.
_assignments_ or _projects_ could be substituted for _situations_, depending on the spectrum of work the company performs, e.g. whether it is involved mainly in new construction/engineering or also in remedial (cracked bridge)and/or disaster (collapsed bridge) situations.

Langenscheidt New College German Dictionary tranlates _Sondereinsatz_ as _special action/operation/mission_, and the term has well-known and in specific contexts very negative military and political connotations.

Perusing a few Web sites (focusing on non-military contexts) confirms that the term tends to convey action that is both exceptional and urgent, often unplanned or on short notice, usually difficult and perhaps dangerous, and may require specialized resources.
More or less direct translations such as _special assignments / projects/ operations_ fail to convey some of these connotations. Hence my suggestion to paraphrase.
German URLs: http://www.bezreg-arnsberg.nrw.de/seiten/presse/1997/243_97.... etc.)
English URLs (total only five): http://theiacp.org/pubinfo/pubs/ProjectRSP/STPevaluation.htm --- http://www.chemieunfall.de/fire.html
(The other three are related to World War II contexts).