After some investigation of the method columnsFromSchema it looks like Firebird (FB 2.5 SuperServer actualy) returns the information about the field type in following form:
u'SHORT                                                                                        '
so it is necessary to add
t = t.strip()
in the for loop (tested)

BTW I have found with some luck the FLOAT type is not detected properly.
u'FLOAT' is recognized as <class 'sqlobject.col.Col'>

How to solve this?

Petr