/usr/include/sipxtapi/utl/ is in libsipxtapi-dev 3.3.0~test17-2.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/sipxtapi/utl/Plugin.h
/usr/include/sipxtapi/utl/PluginHooks.h
/usr/include/sipxtapi/utl/UtlBool.h
/usr/include/sipxtapi/utl/UtlChainPool.h
/usr/include/sipxtapi/utl/UtlContainable.h
/usr/include/sipxtapi/utl/UtlContainableAtomic.h
/usr/include/sipxtapi/utl/UtlContainablePair.h
/usr/include/sipxtapi/utl/UtlContainer.h
/usr/include/sipxtapi/utl/UtlCopyableContainable.h
/usr/include/sipxtapi/utl/UtlCopyableSList.h
/usr/include/sipxtapi/utl/UtlCopyableSortedList.h
/usr/include/sipxtapi/utl/UtlCrc32.h
/usr/include/sipxtapi/utl/UtlCryptoData.h
/usr/include/sipxtapi/utl/UtlCryptoKey.h
/usr/include/sipxtapi/utl/UtlCryptoKeyRsa.h
/usr/include/sipxtapi/utl/UtlCryptoKeySym.h
/usr/include/sipxtapi/utl/UtlDList.h
/usr/include/sipxtapi/utl/UtlDListIterator.h
/usr/include/sipxtapi/utl/UtlDateTime.h
/usr/include/sipxtapi/utl/UtlDefs.h
/usr/include/sipxtapi/utl/UtlHashBag.h
/usr/include/sipxtapi/utl/UtlHashBagIterator.h
/usr/include/sipxtapi/utl/UtlHashMap.h
/usr/include/sipxtapi/utl/UtlHashMapIterator.h
/usr/include/sipxtapi/utl/UtlHistogram.h
/usr/include/sipxtapi/utl/UtlInit.h
/usr/include/sipxtapi/utl/UtlInt.h
/usr/include/sipxtapi/utl/UtlIntPtr.h
/usr/include/sipxtapi/utl/UtlIterator.h
/usr/include/sipxtapi/utl/UtlLink.h
/usr/include/sipxtapi/utl/UtlList.h
/usr/include/sipxtapi/utl/UtlListIterator.h
/usr/include/sipxtapi/utl/UtlLongLongInt.h
/usr/include/sipxtapi/utl/UtlNameValueTokenizer.h
/usr/include/sipxtapi/utl/UtlObservable.h
/usr/include/sipxtapi/utl/UtlObservableImpl.h
/usr/include/sipxtapi/utl/UtlRandom.h
/usr/include/sipxtapi/utl/UtlRegex.h
/usr/include/sipxtapi/utl/UtlRscStore.h
/usr/include/sipxtapi/utl/UtlRscTrace.h
/usr/include/sipxtapi/utl/UtlSList.h
/usr/include/sipxtapi/utl/UtlSListIterator.h
/usr/include/sipxtapi/utl/UtlSerialized.h
/usr/include/sipxtapi/utl/UtlSortedList.h
/usr/include/sipxtapi/utl/UtlSortedListIterator.h
/usr/include/sipxtapi/utl/UtlString.h
/usr/include/sipxtapi/utl/UtlTokenizer.h
/usr/include/sipxtapi/utl/UtlVoidPtr.h
/usr/include/sipxtapi/utl/XmlContent.h