I want to thank every member of team we met at SunTechDays and especially Yegor Yarko for their help to deeper understand what TeamCity is and for.
We had an issue solved by some curved workaround and Egor had encouraged us to make a simple and after all very nice plugin for. In short we wanted to have a sms message when build configuration failed and another one on its recovery to success. Started with Twitter plugin I easily had managed to make what I need. Some problem was with using only classes of teamcity classpath. We have ours ready to do what I need but usage of 3rd libraries requires some special from plugin. For the first one plugin I decided to use what I've got in teamcity. So we've got our plugin.
Thanks again! Now we see for other posibilities to extend teamcity usage for our needs...