In all cases your Determination is retained.

If they add a  new determination then this will be exported to you and will be imported whether or not you select 'All Oriignal; or  All imported;  when you do the import. This will give you two preferred determinations for the same occurrence - not desireable and possibly causing problems in the system.

If they change the determination then what happens depends on  how you do the import. If you use 'All Original' then their change will not be imported leaving your determination as the preferred determination . You may be happy with this, though of course there is  the possibility that the orignators new determination is better than yours or even totally different.  If you use 'All Imported' then there change will be imported, but again you will have two preferred determinations.  To some extent 'All Imported ' is the best option because you can then use the External Filter File  which can be generated when the data is imported to find anything which has changed so that individual entries can be investigated, however, I haven't worked out exactly what can/should  be done here.

There is batch update   'Pref1' which will remove duplicate preferred determinations.    Changes are made on the following basis
   
a. If one of the preferred determination has the same custodian as the current site id then this is chosen. If there is more than one determination which matches this criteria then the one with the latest determination date (based on vague_date_end) is chosen.
b. If a.  fails to produce a result then an attempt is made to find the preferred determination of the owner of the record. If there is more than one determination which matches this criteria then the one with the latest determination date (based on vague_date_end) is chosen.
c. If both a. and b. fail then this will mean that all the preferred determination come from a source other than the owner of the record or the current site id. They could all come from the same Site Id or from a mixture of id's. In these cases the date of determination is used to choose the preferred determination.   
d.  If all the above still fails to find a unique preferred then the preferred will be the first Determination entered.
This can theoretically occur, but is unlikely to occur in live systems.

In the situation you are describing, the Batch Update will leave your Determination as the preferred one.

Something like this was to have been built into Recorder as part of the import, but it no longer seems to be in the list of modifications.  Also  I have just noticed that this batch update needs to be changed to bring the verified indicator  on the ocurrence into line with the Determination type of the preferred determination.