To answer your querry effectively, one needs to understant in what context you are raising the question.
Otherwise to Banks and other institutions, such documents ordinarily would not pass as enough proof of ownership.
However if you hold a plot ownership certificate from a reputable firm pending processing of individual plot Titles - from a consolidated Title in their possession and Name, then you are good to go.
A plot ownreship Certificate is what most middle level real estate agencies confer before they eventually hand you your Title or deed plan to process the Title.
Unfortunately, many unscrupulous and 'connish' agencies have sprung up - issuing Plot ownership certificates/Share certificates over non existent or fraudelently "acquired" land. This is what informs most Kenyans apprehension towards such documents.
The alternative to this is to buy already demarcated and registered land - with its own Title which tends to be substantially dearer!
Dunia ni msongamano..