Observations:
Telephone numbers are at least occasionally screened by CIC in various respects, ranging from Canada411 queries to CIC personnel making a call to the number provided (in addition to seeing reports both anecdotal and references in actual published cases, I personally received such a call while my application was in process, ostensibly to inform me of my interview, which I had received a hard copy notice of in the mail and which was reflected in eCas . . . I am fairly confident the call was really to screen the number to see if it was a working number and who would answer).
The numbers may be examined to see if the area code matches residential information. Work numbers may be verified against name and address of the applicant's employer. If home and work number are the same that can trigger questions about the veracity of applicant's employment information, or be taken to suggest a person is self-employed.
Not every incongruity in such details will result in elevated scrutiny, let alone a problem, but it warrants noting that these are the sorts of details CIC personnel are trained and expected to screen and compare, looking for incongruities and inconsistencies.
This is not to suggest anything contrary to any of the suggestions offered above by others (except to the extent noted below), but more a heads-up that such details can loom more importantly than just constituting contact information.
I would note, however, a few things (based on my imperfect understanding):
-- it is OK to hand write entries into the form (so long as it remains a form to be printed and submitted in hard copy, not online), so where appropriate, it is OK to hand write "N/A" or "none" or "to present" and so on, even though the form does not allow such entries while completing it electronically.
-- my understanding is that "N/A" should be used for items that are Not Applicable
-- "None" should be used, in contrast, where that is the correct answer (thus, for example, for an applicant who has no cell phone, "none" should be entered for that number, not "N/A")
-- it warrants recognizing, however, when it comes to many of these details, the difference is probably of relatively little import, and this is true of some blanks even, how the particular items fits into all the rest of the information looming as the larger factor in whether a question or concern is triggered
Entering all blanks for telephone numbers is bound to invite questions, for example, but for a person who reports being a student at the time of applying, a blank for "work number" probably works as well as "N/A" or "none;" in contrast, for a person who reports being employed, a blank for the "work" number is likely to draw some attention or questions.
Context matters. Almost all information has relational import depending on other information in the application.
Details matter. Individual details do not loom large on their own but how they fit together or relate to one another is of much importance.
Ultimately CIC considers all the information provided. Certain information may be essentially contact information, but CIC can and often will use that information in its screening and evaluation of the applicant and the applicant's case.
