В общем, разобрались.
Шаблон Excel-файла для вставки в него текста через буфер обмена, открывался методом SysExcelWorkbooks_XP.open(...), в котором 4-м параметром идет формат разделителя, по умолчанию там стоит _format = 5 (без разделителя). Проблема разрешилась передачей _format =1 - в качестве разделителя используется символы табуляции.
X++:
public boolean open( str _fileName,
int _updateLinks = 0, // Specifies the way links in the file are updated.
boolean _readOnly = false, // True to open the workbook in read-only mode.
int _format = 5, // If Microsoft Excel is opening a text file, this argument specifies the delimiter character.
str _password = '', // A string that contains the password required to open a protected workbook.
str _writeResPassword = '', // A string that contains the password required to write to a write-reserved workbook.
boolean _ignoreReadOnlyRecommended = false, // True to have Microsoft Excel not display the read-only recommended message.
int _origin = #xlWindows, // If the file is a text file, this argument indicates where it originated. See #Excel for modes.
str _delimiter = '', // If the file is a text file and the Format argument is 6, this argument is a string that specifies the character to be used as the delimiter.
boolean _editable = false, // If the file is a Microsoft Excel 4.0 add-in, this argument is True to open the add-in so that it’s a visible window.
boolean _notify = false, // If the file cannot be opened in read/write mode, this argument is True to add the file to the file notification list.
int _converter = 1, // The index of the first file converter to try when opening the file.
boolean _addToMru = false, // True to add this workbook to the list of recently used files.
boolean _local = false, // True saves files against the language of Microsoft Excel (including control panel settings).
int _corruptLoad = 1, // See Microsoft description.
boolean _openConflictDocument = false // True to open the local conflict document.
)
{
...
}