From researching about "shadow" functions, it can be concluded that they are either destructive or supportive to your main functions.
In the case of the INTP:
The dominant function of Introverted Thinking can be supported by the role of Extraverted Thinking. In this instance, once you have applied Ti, Te will help you further to develop your analysis, plan etc. So in other words, you can be competent in applying Te however it will be used with narrow application since it requires greater strength to use it independently.
They in a sense follow your dominant functions pattern, with the exception of a reversed E/I mode. So depending on your individual development, Te and Ni might be functions which are used easily for a handful of INTP's (bearing in mind that shadow processes strengthen over time).
The shadow processes are by far, not the most lethal or worst processes if they are used consciously. (Ask yourself, would my Ni be weaker then using Fe more openly.) Chances are in the INTP, not really because both Feeling functions aren't used considerably and so Shadow processes just determine the helpfulness towards the Dominant Functions as opposed to actually being a set pattern of unproductive modes.