  Aims: We present a quantitative study of a new data set of high redshift Type
Ia supernovae spectra, observed at the Gemini telescopes during the first 34
months of the Supernova Legacy Survey. During this time 123 supernovae
candidates were observed, of which 87 have been identified as SNe Ia at a
median redshift of z=0.720. Spectra from the entire second year of the survey
and part of the third year (59 total SNe candidates with 46 confirmed SNe Ia)
are published here for the first time. The spectroscopic measurements made on
this data set are used determine if these distant SNe comprise a population
similar to those observed locally. Methods: Rest-frame equivalent width and
ejection velocity measurements are made on four spectroscopic features.
Corresponding measurements are presented for a set of 167 spectra from 24 low-z
SNe Ia from the literature. Results: We show that there exists a sample at high
redshift with properties similar to nearby SNe. No significant difference was
found between the distributions of measurements at low and high redsift for
three of the features. The fourth feature displays a possible difference that
should be investigated further. Correlations between Type Ia SNe properties and
host galaxy morphology were also found to be similar at low and high z, and
within each host galaxy class we see no evidence for redshift-evolution in SN
properties. A new correlation between SNe Ia peak magnitude and the equivalent
width of SiII absorption is presented. We demonstrate that this correlation
reduces the scatter in SNe Ia luminosity distances in a manner consistent with
the lightcurve shape-luminosity corrections that are used for Type Ia SNe
cosmology. Conclusions: We show that this new sample of SNLS SNe Ia has
spectroscopic properties similar to nearby objects. (Abridged)
