Hurray!
After three days of unsuccessful googling and asking this question everywhere :-) I tried to investigate it myself and at last, I have found a way to do it!
It appeared that it is quite easy to map it by hand. For that you have to make 2 changes in the BDC model file (xml with a .bdcm extension):
Add property with the name of Office item type to the entity
<Entities>
<Entity Name="AbsenceCalendar" DefaultDisplayName="AbsenceCalendar" Namespace="MyNameSpace" Version="1.0.0.0" EstimatedInstanceCount="2000">
<Properties>
<Property Name="OutlookItemType" Type="System.String">Appointment</Property>
...
</Properties>
...
Map necessary fields to the Office Item Type. For instance, for mandatory fields of Appointment Office Item Type it could look like
<Method Name="ReadSpecificAbsenceCalendarEntity" DefaultDisplayName="Read Specific AbsenceCalendarEntity" IsStatic="false">
......
<Parameter Name="@AbsenceCalendarEntity" Direction="Return">
<TypeDescriptor Name="AbsenceCalendarEntity" DefaultDisplayName="AbsenceCalendarEntity" TypeName="Microsoft.BusinessData.Runtime.DynamicType">
<TypeDescriptors>
<TypeDescriptor Name="Title" DefaultDisplayName="Title" TypeName="System.String">
<Properties>
<Property Name="OfficeProperty" Type="System.String">Subject</Property>
</Properties>
</TypeDescriptor>
<TypeDescriptor Name="StartDate" DefaultDisplayName="StartDate" TypeName="System.DateTime">
<Properties>
<Property Name="OfficeProperty" Type="System.String">Start</Property>
</Properties>
</TypeDescriptor>
<TypeDescriptor Name="EndDate" DefaultDisplayName="EndDate" TypeName="System.DateTime">
<Properties>
<Property Name="OfficeProperty" Type="System.String">End</Property>
</Properties>
</TypeDescriptor>
.......